Why is Trump going after protestors? Has there been a lot of illegal protesting recently?

Trump just posted (on x or truthsocial):

"All Federal Funding will STOP for any College, School, or University that allows illegal protests. Agitators will be imprisoned/or permanently sent back to the country from which they came. American students will be permanently expelled or, depending on the crime, arrested. NO MASKS! Thank you for your attention to this matter."

What's he talking about? Why is this a big deal right now?