Here's why I think that the Modernist Heretics finally pulled the trigger.
They were getting increasingly concerned that the Motu crowd were growing in numbers. Originally it was intended as a fly trap to suck those back into the Conciliar institution who might otherwise be inclined to become Traditional Catholics. But it was working in the opposite direction.
It was intended to make Traditional Catholics less Traditional. Instead, it was causing Conciliar Catholics to become more Traditional, and it was also serving as a "gateway" to true Traditional Catholicism. That's why there's this huge emphasis on not having any more, not having newly-ordained priests offer the Tridentine Mass, etc. They were worried about the growth of the Motarian movement and its slouching toward Tradition.
Young people who weren't around/don't remember pre-Summorum are going to be too blackpilled. I think the young people in particular are going to go SV or SSPX, a lot of older people who've had this whiplash multiple times will just go NO.
I didn't see if this was posted here, but everyone knows about TM. I had no idea there were 41 Latin Masses in Detroit. That's a lot! I thought New York was good with less than ten.
Getting fresh blood in the door that puts money in the plate is going to be an issue. In the next 20 years or so I wouldn't be surprised if they introduced some sort of Summorum thing again just to get a financial base situated once the boomers and silents are all gone. You'd think they would have been more worried about money rather than ideology but that shows just how wicked this motu is.