From two months ago, Stevens on the "news", talking about her endorsement of El-Sayed.

After endorsing El-Sayed, Stevens says the time for negativity is over: "Differences were aired out"

Yep. That's probably a part of what led her to agree to the joint appearance in the first place. She was clearly willing to take some affirmative steps to get him elected. But as you pointed out, TYT went hard on a very....let's say a strident ad on the topic of Israel. It's very possible that this ad, and El-Sayed's reaction to it, rekindled some of those differences that were previously aired out.

El-Sayed had been trying really hard, it seems, to avoid having Israel resurface as one of the "keystones" of his campaign, as you called it before - and I expect that was one of the differences that had kept the camps apart. So having an ad that is entirely focusing on Israel as part of the closing argument, even one from an outside group, didn't help - and then El-Sayed's reaction to it didn't help, either.