It is just corporate life, not you
A colleague of mine returned from a 4-week vacation yesterday. In that time, our boss left for a new company. Maybe 3 minutes was spent catching the colleague up on that before we all returned to our usual work.
When the boss left, there wasn't a lot of fanfare or discussion. He cleared out his office, we spent maybe a half-hour wishing him well, and then he was gone. And unless you are maintaining an ancient backend system he helped run, little changed. And he spent some 8-10 years there, a phenomenally long time for a developer. Within 3 years, there will be nobody who worked with him still there.
When I have left jobs, there have been a few handshakes, some chit chat, and then we each went our separate ways to most likely never meet again. People stopped asking for my opinion around the beginning of August for my summer jobs as it didn't matter as much as I was leaving.
If they know that you are on their way out, they may be already of the mindset that you are gone. They then stop planning future projects with you, as you won't be there for those projects. They stop giving you work where expertise will be needed down the road. Training you is a poor investment as again, you will leave before you really get to use it much.
All of this is because as soon as you stop being co-workers, most connection utterly evaporates. And you will be imminently evaporating.
What you do depends on your work environment and your goals.
- Need the salary? Just stay put unless you can find another job.
- Can you re-apply your time at work to other things? Use it to learn stuff from Udemy.
- Are you just being given work which the other developers do not want to do or consider to be low priority? Go find a new job for the 7-8 months. Just don't tell them you will be leaving.
I would not job hop now just because it may look strange to hop yet again after only 7 months in a company and some may label you a job hopper. But this depends on your area.
EDIT: I stumbled upon this answer again and thought I would post an update. Nobody has mentioned my old boss in months. 8 years of his life and he is effectively departed from institutional memory. About 1/3 of the current team never even knew him as we have had other departures and replacements. Such is the corporate life.
EDIT 2: It has been 18 months since he left. In that time, I left. Several other co-workers left. His boss got promoted to another division. The heads of the teams he worked with the most have all left. Nearly everyone from the project he assigned me to is gone. There are maybe 5 people left in the building who knew him all that well. Things change quickly.