They didn't plan to join NATO. Ukraine had a single digit percentage interest in NATO before crimea.

Moves were being made to join NATO back in 2008, but progress was shelved when pro-Russian president Viktor Yanukovych was elected. He was driven out of the country, Russia took Crimea, and then NATO seemed like a particularly good idea.

Russia doesn't want Eastern European countries in NATO, because it makes it much harder to take them over.

I would also add that it takes them out of the Russian sphere of influence, which is Russia's main concern. Why take over a country if they cooperate with you?

NATO is a defensive alliance, and is no danger to Russia except for their imperialist goals. Best example of it is after Finland joined NATO Russia removed their troops from that border. That's right Russia now has less troops there than they had when they were imaging Ukraine.

Well, yes it's defensive. No NATO country will attack Russia. However, I'd argue that Russia sees it as more than defensive. Each country that joins the alliance is one less country that Russia can dominate de facto. It's militarily defensive, but that comes after an economic amd political offensive that removes the country from Russia's influence. Now you might think, well, those countries entered that agreement voluntarily, and I'd say you're correct, but Russia doesn't care how it happened. They were taken from Russia as far as Russia is concerned.

I'd also argue that the troop removal from thr Finnish border may have more to do with needing troops in Ukraine than it would defending St Petersburg from Finland.

And one last thing: even if it was true, since when Russia can decide for sovereign nation who they form alliances with? The excuse to invade looks exactly as the same bullshit Nazi Germany invented with Poland (both claiming to save German minorities and also that was actually planning to invade Germany). They are not even original.

Well they did decide in 2008 in Georgia and they just did in Ukraine. Yes, their justification was mostly BS for domestic consumption, but that doesn't really matter in the end. Other imperialist countries do this, like the US, China, France, etc, but they're more subtle and you're in the West's media bubble, making it really hard to get an impartial source.

As much as I agree with your overall arguement, I just want to point out that the main reason why russia now has fewer troops along the finnish and norwegian border is because they needed to reinforce the donbass leather factory. If they had the resources, the manpower on the border would probably remain the same.