I don't disagree with your details, but I am really not sure why the alternatives (Obama, Clinton, Biden) were somehow seen as tougher on Russia? All the invasions from Crimea in 2014, and 2023 were not under Trump administrations and the response from the US then was not effective at all.

It's debatable: funding and supporting a proxy since 2023 was a pretty effective way to keep Russia into a quagmire for years, seriously affecting their military, draining their finances, and isolating their economy - to the point that any non-military activity outside of the country has basically disappeared. Short of direct engagement, which is unfeasible due to MAD, it basically was the strongest response.

(2014 is different, in the sense that it was always going to happen if Ukraine ever managed to escape Russian orbit, and more or less everyone knew.)