The first times I saw "cis" being used, it was a punch back against anti-trans slurs; the use was intentionally pejorative but it was justified. A bit like calling a white supremacist a cracker.

I suspect the wider use beyond this aim was to teach transphobes a lesson by giving them an undesirable label ("cissys" was used if offence was sought) in an attempt to create empathy. The "it's a technical term" argument did offer a funny balance to the "biological" argument which helped de-tooth some anti trans talking points..

Of course, this approach also probably drove more of the indifferent to oppose the trans movement, rather than garnering empathic support.

It likely did more harm than good, and is likely a hill a lot of folks are going to die on. Then again, maybe that was the point?