I bet that Evil Jerry is behind Evil Morty
I had a concept where the Beth of their universe died in some Rick-related incident, and the Jerry manipulated everyone into thinking that it was Ricks doing.
Already hating Rick, and being as lethal and assertive as c-137 Jerry is harmless and useless, Evil Jerry set his sights on one goal: killing all the Ricks of the citadel, and eventually the multiverse.
He gave his Morty (evil Morty) the job of disposing of their Rick and infiltrating the citadel, which he did (close rick counters)
What he hadn’t counted on, was C-137 becoming such a thorn in his side.