People forgot how long it took the other world wars to really get rolling. (Presumably because they weren’t alive when it happened.)
I’m also of the opinion that unless something happens to de-escalate this conflict it will inevitably draw Europe, the US, and China in.
They’re not stranded because the part of the capsule that isn’t working has multiple redundancy and is intended to burn up on reentry anyway.
Starliner is perfectly capable of leaving the ISS whenever they want, but they would be unable to continue collecting data on the thruster shutoff (again, because it would burn up in the atmosphere).