It seems that the question has been treated a bit harshly indeed. The "trivia" close-reason is precisely to protect against empty brand identification that contributes nothing to the appreciation of the work. Yet you make a good case for why it is relevant to the episode, especially since it's an educational program.
While we do need the close-reason to protect against empty IMDb lookups and irrelevant "what car's that dude driving" things, this community has also grown a bit over-anxious about possible trivia questions over the years, in addition to the general inability of SE sites to operate effectively on somewhat vaguer rules. I would argue there could certainly be made a good case for your question not being such in its current form. Add to this, that your improvements in this regard also came after it had already attracted close- and downvotes, and there can be somewhat of a bandwagoning effect in these cases. I don't think it had much to do with it being a kids' show, though.
But another problem that adds to this is, that it has also been downvoted to quite some degree, for the same reasons of a community having grown tired of low-quality contributions. While this certainly needs to be dealt with in the bigger picture, in your specific case this also means even if we reopen that question, we will end up with an open but unjustifiably low-scored question since there's not a big chance all the people downvoting it will revert their votes after seeing your possible improvements. So it's really difficult to decide what to best do with that question now and to be honest, maybe deleting it and rewriting it entirely (especially with emphasizing the educational viewpoint) would even be preferable, although I know that means quite a bit more work for you.
I'm really sorry that this happened, but I think you got jumped on a bit here.