This makes no sense, sorry. If NATO was truly hellbent on invading Russia and just threw 5-10% a year into building up a huge tank army, Ukraine wouldn't have m

This makes no sense, sorry. If NATO was truly hellbent on invading Russia and just threw 5-10% a year into building up a huge tank army, Ukraine wouldn't have made a difference. Not to mention that the Baltic route towards Moscow is shorter. A Russian puppet state in Ukraine would've given Russia an "early" warning of about a week. Would they be able to muster a defense in a week? Of course not. Would they be able to conventionally defend against NATO? Of course not. That's why their doctrine has been "any conventional invasion against Russia will be answered with nuclear weapons", and that's a great deterrent. That nobody actually wants to invade Russia is the cherry on top of the "if you invade, the world ends" threat. The Russian invasion certainly surely has plenty of reasons, but "we're afraid of NATO" is all the way down the list. Much higher will be: domestic politics, fertile grounds for farming, natural resources to exploit, increasing the size of the population you can steal from, and likely also a generous amount of "I'm old, I want to be remembered as the man who returned Russia to former USSR-glory".