It's not my opinion. The US admitted it's a proxy war and there's ample evidence, but it's too late.
Ukrainians voted for Zelensky because he promised peace, but now, they endure the numerous, relentless casualties of a wartorn country for the next few generations. It's a god damn travesty that could and should have been avoided. However, NATO-US' written response to Putin was, "we don't negotiate".
Putin decided the response was worth the mass deaths and devastation, and so did NATO-US, but did Ukraine? No. The people did not want a civil nor foreign war, but the country wasn't involved in the pre-war negotiations - it didn't have a choice.
The premise Putin intends to take over Eastern Europe and the world through military intervention doesn't have a resolution, and a forever war suits the weapon manufacturer lobbiests and US hegemony goals perfectly. Sustaining Russia's attention in Ukraine eliminates a competitor while fueling the only US global market producing capital.
The theory you suggest is an assumption that isn't supported by solid evidence, but our government won't address Russia's stipulations. It's in Ukraine's best interest to end the misery ASAP, yet there's no movement by global powers to pursue any negotiations, and even if your theory is correct, isn't it worth investigating potential lifesaving resolutions?
What Russia did to Georgia mirrors what's happening now, and Ukraine deserves peace, but we are pushing war.