They are clearly not applying a blanket suspend all Russian accounts policy but rather one that attempts to address accounts with some kind of tie to sanctioned Russian companies. Github/Microsoft is a US based company and likely feels legally compelled to take these actions.

In fact they say this:

At the same time, we are taking action to support our platform and comply with the many government mandates you’ve likely read about in the context of this war. Our legal team examines such mandates thoroughly, and we are complying with export controls and trade regulations as they evolve. This includes implementing stringent new export controls that are aimed at severely restricting Russia’s access to technologies and other items it needs to sustain its aggressive military capabilities.

That's the end of it full stop. I'm sorry this inconvenienced some open source project but this is how things like an account suspension work. This is not the death of open source or the fault of Github.

Everyone knows where the real blame lies and rather than bitch about being inconvenienced by the response, the open source author should direct their anger there. Yes, "innocent" Russians are getting swept up by the response and that sucks.