taking a strictly realist view, I think it's obvious why Russia feels threatened - because they are threatened.
a concise version of what I was saying, minus the historical context
always more useful to view geopolitics thru realpolitik lens. regimes act in what they perceive to be their self-interest. those actions may/not be morally objectionable.
do think historical context is important here. Russian rulers have always been concerned w/access to year-round ports, Central Asia (Great Game etc), influence in E Europe, etc. add inherent paranoia of siloviki ruling class, post-Cold War tension lingering resentment over American/W European role in absolute mess of 90s Russia, to traditional Russian fears and losing my edge worries over diminished global role. easy to forget Putin was (still is to some extent? idk) v popular when he came to power, stabilizing things, restoring Russian pride killing many, many Chechens. I'm sure many Russians, even some opponents, appreciate him standing up to the West, if perhaps not the repressive state security apparatus, murdered journalists, corruption, etc. + obv no one should be surprised that a regime of ex-KGB guys is totally into disinformation and information warfare.