Speaking as a Russian who grew up in the 90s, NATO was never a real threat to post-Soviet Russia. Our "national patriot" political faction made it into a threat in its propaganda because they needed an existential enemy to build their ideology up on.
Perhaps you can ELI5 because I was under the impression Ukraine was a sovereign nation. Free to pursue any alliances it wishes. And that its 1991 borders were acknowledged in exchange for yielding nuclear weapons to Russia.
Here’s the president, himself, explaining what’s going on: https://www.newsweek.com/joe-biden-resurfaced-clip-russia-ba...