Yep, I made comments similar with meme addressing it. But people downvote them to hell.
Though the deal was actually more for NATO to NOT EXPAND anymore past EAST GERMANY. Putin allowed it for some time, but enough was enough.
NATO was established to combat the Soviet Union. Its purpose had already been served after Soviet Union has been abolish. NATO has still been taking in countries in the last several years even after Soviet Union was abolish.
1999 Poland, Hungary, Poland
2004 Bulgari, Romania, Estonia, Latvia, Lithuania
There are many more, but these prime ones are the ones that expand Eastwards from Germany
The 1999 ones obviously have been centered around the old Warsaw Pact which was the first time NATO ignored their verbal promise they made and not the last with the following 2004 nations.
If Ukraine joins NATO it will further encroach along Russia's borders leaving them little to defend themselves should the West pose a threat to them in the future.
If Russia takes Ukraine it will solidify a strong defensive front against NATO.
Also in 1990 before any of these expansions there was the pledge between NATO and Soviet Union. They would get back East Germany, but NATO CANNOT MOVE ANOTHER INCH PAST EAST GERMANY. Yes, they gave that county back and pulled out of it to put an end to the war. This pledge was also spoken publicly by NATO's secretary general in a speech in May 17, 1990 in Brussels.
In all fairness NATO pushed this to happen and Putin has repeatedly told his demands for NATO to dissolve and they just ignoring it. Ukraines attempts to joining NATO was the final nail in the coffin.