Stiffing the R's on his promises/oral contracts of the various things he would do if allowed to continue in the Speaker's chair, would certainly have been enough for me.
The challenge would have been to accurately calculate the dedication of the Rino's and weigh that against the damage to be realized by a Dem Speaker. Not a good spot to be in.
The rats could and did put up the most radical leftist without any worries about any D voting against the majority. The GOP always has a group of traitors ready to go. The party has nothing but contempt for the base.