The boycott was about something, normal users don't give any fucks about: Third party apps basically exclusively used by moderators to automate banning and censoring.
Users were also already pissed about being banned from subs based on which other subs they are in.
And the boycott was mostly experienced by users as moderators closing down subs without caring at all about what the actual users think about that. Sub mods in general already had a reputation as being narcistic and unreasonable to the point that they there and still are used as a meme.
So naturally, user sympathy was rather limited.

In addition to lack of user sympathy, Reddit was never actually at risk of being replaced by anything else. Where would the users go to?
Lemmy and others are the niche's niche; I still add Reddit (not Lemmy) to my web searches because that's still where the content is. Reddit is massive and for most topics there just is nowhere else to go to. The network effect is real; size actually does matter a lot. It's the same reason, YouTube can get away with their enshittification.