Putin did not want NATO close to his borders. But he wants to extend his borders closer to NATO. 
The only lesson here is you showing us once again you are a complete moron.
Russia has been invaded via neighbouring countries in the past and he wants to take over areas in order to plug the gaps the invasions took place. That’s provides the buffer as it means NATO can’t get to Russia straight away.
Russia is not under threat of invasion. That’s the main argument against Putin’s plan today.
Russia’s demographics suck balls along with their lack of education. That’s the argument For why he is doing it now. All his population are old and not in physical condition meanwhile his young population are unskilled and uneducated. He is already drafting 50yr olds…… he can’t wait another 10yrs because they’ll be 60…..
The real question becomes WHeN he takes over the Ukraine, then what? His next battle is directly with NATO and as he is already desperate, that same desperation might begin to rationalise the use of nukes when faced with the realisation if he doesn’t go all the way he will be sanctioned to death by the world.