Transfems are trying to disempower afabs not so that amabs and afabs have equal group powers in queer/progressive/leftist contexts, so that there is no longer domination by any agab, but they are specifically trying to establish amab domination and therefore subjugate afabs because they fear that if afabs are not under amab control they will almost inevitably reconstitute themselves as a terf political force, and therefore reproduce transfem oppression.
The subjugation of afabs to amabs is therefore seen as a way of minimizing the risk of the terf threat, a way to keeping it under control.
You have to get it into your head that transfems see afabs, whether cis, trans or non-binary, as a terf threat.