[verdverm]

Russia has plenty of oil & gas in their existing territory. If anything, Putin wants to prevent Ukraine from becoming the supplier to Europe

Most experts see the reasoning as Putin wants a sphere of influence, and since no one is volunteering besides Belarus, he decided to do it by force. It's more Make Russia Great Again (like the times of czars, not soviet union)

[quantified]

Preventing Ukraine from becoming a supplier still fits the parent comment.

[verdverm]

Except for the last sentence

[quantified]

This one: "Sounds more plausible than pure ego"? We seem to believe ego well enough (we certainly succumb to it), so if that's what you refer to, I do take your point.