I think why theater kids specifically are getting the blame is because, while there were always TMI autistic nerds trying to drag normies into listening to their rants about their Special Interests, the norm used to be that nerds knew they were nerds, and kept their nerd shit under the table because they knew it was niche.
Where theater kids come in is when you have nerds, then give them the idea that they should take up performative acting. Now, in their mind every social interaction has become a rehearsal to hone their acting skills, and they’re still nerds, so they now not only seek out people to interact with, but talk to them about nerd shit because that’s the main thing they know about. Give these people money to do this, and enough of a platform, and you get what you have today.