He was considered a core, visible member of the rationalist community from well before the split. For better or for worse he is considered a figurehead of the movement. With the acrimony of the split there was no way he was going to escape unscathed no matter which side he ended up on just by sheer visibility of his writing.
But it's not rationalists mad about this split who seem to have outsized vitriol for him. It seems to me that it's people who were not involved in that community to begin with.
My read has always been that the angry folks were always rationalist adjacent even if they weren't rationalists themselves. There's a lot of people in my IRL network, for example, who are 1-3 degrees of separation from Scott or Yud but have never posted about them or in the rationalist blogspace at all.
