If so, why would SpaceX have so rapidly & aggressively moved to restore Ukraine's communications capabilities in the early days and weeks of the current war, and maintained them ever since?
Based on some old tweets, I think Musk believes Putin wants to use nuclear weapons. Then, the army put some pressure on him to keep supporting Ukraine, but he is still also working on his own. I'm sure he could block the Starlink terminals Russian army is using, if he wanted to try, for example.
Plausible. It's not how I imagine them engaging with their defence contractors but I don't actually have a clue how it works. One supporting point might be if there were any other companies treated similarly, like if Lockheed Martin was ordered to immediately ramp up production of relevant types of military hardware, and told that the details (contracts / payment / etc.) would be sorted out later.
An opposing point would be the fact that the US and its allies knew an invasion was likely well in advance. Yet the initial Starlink 'roll out' seemed pretty ad hoc, with SpaceX organizing its own logistics. But then maybe the allies didn't expect Russia to be so effective in disrupting the existing military comms infrastructure.