No one likes a Negative
In general, people don't like people who are constantly negative.
Someone constantly complaining about [processes, people, technical skills, etc] will result in a quite negative image of the person.
That sort of person just isn't fun to be around. Trust me, I know, when I was younger I could have written your post. It was so obvious to me how everything everyone else did was wrong/bad/could be improved. It was my mission to inform them!
Being awesome is not the same as being a good team member
Being able to work with people is just as important as being excellent technically in most places (as you just found out). Most people, by definition, are not "A" players.
Let's pretend for a moment I'm a coworker of yours feeling your attitude:
- I wish we hadn't hired PicPic, he's good at his job but is a jerk. He makes me feel incompetent and came here and started telling us how to do our jobs even as a new employee. He thinks he's above this job and acts like we're a bunch of idiots. I wish he's stop telling us how we need to learn/grow/improve..
Based on how you wrote your question I think this is quite likely how your team feels about you. You can't act condescending/superior to people and try to fix them without them feeling that way.
Now, let's imagine I'm your boss.
- PicPic is great technically, but really struggles with people skills. He wants everyone to just adopt his ideas because the are The Best and doesn't seem to know how to work with or persuade people. I'm not sure if he's actually a good add to our team or not, he's demeaning and arrogant and people feel it. We were delivering what we needed before and he's causing resentment amongst my team, which might change that too.
You have to be able to work with others effectively. Many if not most jobs will have you working with people of varying skill levels. This answer to a related question applies here, too. People seem to think "I'm awesome, everyone will just respect my awesomeness regardless of anything else!" but it turns out, that's not how it works.
Who am I???
People probably perceive you very differently than you think they do.
You might feel you are "just stating facts" but if this is done poorly it can come across really negatively or critical. Answering questions can either come across as an earnest mentoring or a demeaning dismissal.
I would encourage you to do some self evaluation about how your coworkers/bosses likely perceived you - not what you were intending to communicate, but how they probably interpreted your communication.
Likely you will find this surprising and if not, it probably means you need more of it.
Did I make a mistake saying I was dissatisfied with the job?
Yes, when your reason for being dissatisfied is basically "I think my coworkers suck" and "I'm too good for this" you probably should be very careful in how you say it.
Keep in mind that you need to frame things in a way which is mutually beneficial. This might feel like BS, but you need to frame things in such a way that your employer sees the value in what you are doing. "I'm bored" vs "I think I could be better utilized doing X, Y, or Z" etc.
If you want to move into an architect position someday (also, at age 26 you are very young to be wanting that in the near future, experience in working on a long-term multi-year project from start to support is very helpful for architects), you need to figure out how to find a way to do those things in your current job. But you can't just start doing them because it benefits you - it has to benefit others and your company.
The best way to do this is find things you want to do, document them, and then basically just suggest to your boss, "we sometimes have [problems, issues, etc] with [x, y, z], I was thinking it'd be a good opportunity for me to try to resolve them by doing [a, b], what do you think?"
Managers love saying yes (or tweaking things). Presenting your interests as a way to further their goals is nearly an auto-yes from most managers (wait, you want to add more value and do the hard work of defining the work, too?! great!). This answer to a question of mine is also pretty useful, as it suggests ways to approach career development with a non-helpful boss.
Regardless of how you feel about things, you need to at least try to communicate to your boss why things are in their best interest to do. Saying, matter of factly, "we need to do X" [because it furthers my career goals] will not convince many. But phrased like I say above will do you wonders.
Too often we focus on the how/what of our suggestions and ignore the impact of them. No one cares about a next-best-thing, but people do care about developer time, money, and cost (as examples, most workplaces have plenty of problems which need solving too. Approaching solutions by the things your management care about is really effective and persuasive. Are people wasting time because of something? Keep track of it, and say, "we can save 6 man-months of work a year by removing this problem by X."
All this works both ways. You are more effective in your job because you are better meeting the goals/objectives of your boss(es) and that also lets you accomplish more of these things you want to do.
A manager/employee relationship should not feel adversarial. I will say that you learned that employees are much less than needed/respected by companies, and it's always good to keep this in mind throughout your career. Your job matters a lot more to you than your boss/company.
Did I make a mistake saying I was looking for another job?
You should never do this unless you are prepared to not have your current job or have really, really good reasons to trust that your current employer won't react badly (hint: 1 year seniority isn't it).
What's wrong with looking for another job, if you are still doing your best?
When a new employee who basically thinks everyone is an idiot says they are looking for another job, it doesn't take a genius to realize they are not really committed to their current work.
Waiting for them to quit isn't ideal in most cases, especially if they are (likely) a negative influence on team morale.
Perhaps I can understand why I've been fired, however: why wasn't I fired earlier? I though it was obvious to them that I wanted to quit sooner or later.
Keep in mind, if there was doubt about you being a negative on your team, it's likely this is a great excuse for them to go "finally we can just get rid of him." If you work for a small company, a single person can cause a lot of problems for everyone else. Everything you wrote suggests this to be the case.
Or maybe your boss and the CTO/CEO thought you might grow in your people skills...