Commenting based on title, I did see a random unexpected (less popular, this is a friend of friend of beto I'd describe them as) celeb switch sides over this. So it may be legit that people are leaving the left a lot

I'd speculate that it's possible the outright support of assassination (of literally NOT Hitler) is actually a step too far and that a lot of people don't want to be in those crosshairs for simply saying the wrong thing.

Not so much they agree with MAGA or are against assassinations entirely, just that they are concerned with "purity spiral assassination culture" if I could describe it as such: a little bit too indiscriminate of violence against people who might simply not meet the whim of their standards

I think there's also a maturity some on the left have that some of our families have not people on the left and right, and people that have switched sides at times. By killing your political opponent, you give them no time to change or repent. (I have in mind Newsome who had Charlie on his show this year; he acknowledged his son liked Charlie and both of them definitely strongly disagreed on the issues but were still able to have a conversation about things)