The resources needed to do this. Compromising and paying Twitter staff, the practical, technical know how (and it's cost), and that no real attempt to profit from this has been made?

I don't think that sounds like a financially motivated crime at all. As a crime it has more in common with the proverbial 'horse head on the bed', than a sophisticated heist. I think this was done to shake confidence in the perceived invincibility of Silicon Valley and FANG like companies particularly.

But then any number of well resourced 'political' actors would love to send that message to the large tech companies...