Have the presenter preview the presentation with you when the person is your junior and help him or her strengthen it. That is a part of your job as their boss. It is certainly what my bosses did for me when I was junior and what I do for people junior to me now.
What you want to do is make certain the person doing the presentation gets more in-depth knowledge to be able to answer questions, so make sure to give that knowledge to that person on the topic at hand and tell them to be free to call on you if the questions get outside the area they are familiar with. You might even give the presenter a hand signal you will use when you would like to add something. It looks better if he calls on you to add something than if you barge in. You are also then able to correct any errors or misconceptions before they are made in public.
My view on giving presentations (and I have given thousands since I used to teach) is that you should have roughly twice as much knowledge on the subject as the amount you are presenting to be able to handle questions.
Now you are going to have to contain yourself when helping the junior prep for the presentation. At all times, you need to be thinking about what the audience needs not how much you could say about something. An audience new to a subject often doesn't yet have the background to understand all the nuances you know and to give them to them too soon will likely make you lose their attention and they won't learn what they need to know.
If you really need to answer a question during the presentation that you felt was not answered good enough, then start with a polite phrase like, "To add some more detail to that..." But remember, the level of detail you know is not necessarily the level of detail that people just learning the subject need to know or are ready to know. So only do it when the knowledge is critical to what they will be doing as beginners in the subject. And pay attention to the way people are responding. If eyes start to glaze over, then it is time to stop.
Then you also need to work a bit on dealing with being the "Smartest person" in the room. When you think (even correctly) that you are the only person in the room who is smart (and that smart is the best and highest value a person can have), then that will make you project an unconscious arrogance which will turn people off.
One thing I read once was that it is very hard for people to communicate with people who are not within about 20 points of their own IQ and I have found it to be true in many cases. This make it hard for very smart people to communicate with less smart people.
So if you are truly extremely smart, you have to make an effort to learn how to communicate at the level that other people will understand. The onus is on you for this as you can't change other people, only yourself. You need to tone down your vocabulary and think more about what they need to understand that what you want to present to them.
I've worked with genius level people and people who were not very smart. All of them had value as people and as co-workers. You are not better because you have more knowledge. I think from what you wrote, you are starting to tend in this direction, but it is something you need to consciously do. And it's tricky because you don't want to come across as talking down either.
Now when the presentations are from outside your group, then the calculus of when to add detail to an answer is different. You want your people to shine and you want to support them only when they are floundering. Outside your group, you want to consider the politics of the situation.
Do you need to make the point that your part of the organization has the real expertise in this area? Then you may need to jump in more often. Is the presentation to senior managers who are not really concerned with the nitpicky technical details, maybe less often. Is the person doing the presentation your manager? Definitely, less often. If you have concerns about something he or she said, then approach in private and have that person send out a clarification in an email. Is the person doing the presentation someone who you will be working closely with or a client? Be aware of the nuances of political realities as much as you are aware of the nuances of your technical subject.