1 - Nato was formed as a defence block against the "second Russian Empire" i.e. the Soviet Union and is still around to counter the budding "third Russian Empire".
2 - even since being conquered by the Mongol Empire Russia has been paranoid about the possibility of some conquering entity crossing its long border to rush into its vast territory. They want mountain ranges, sea or some other barrier between them and that potential enemy. If none of the sort can be had they want a buffer zone - they call it neutral states but in reality they mean vassal states, e.g. Belarus - between them and "the others". Those vassal states were gathered into a "counter-NATO" in the form of the Warsaw Pact.
3 - after the dissolution of the "second Russian Empire" and with that of the Warsaw Pact the former vassal states, fed up with being subservient to their oppressive neighbour bully took their chances and ran with it by joining NATO.
4 - Meanwhile Russia depopulated, was taken over by a new (old) gang of kleptocrats under first Yeltsin, then Putin while "the West" was busily "spreading democracy" by bombing and invading countries which were deemed to be essential for their economies by virtue of them being rich in natural resources. Some people and companies got richer, many people died and democracy was far to be found. This provided the Russian kleptocrats with a credible excuse for creating a new version of the old "us versus them" narrative: NATO is just like the Mongol Empire out on conquering our land to sap and impurify all of our precious bodily fluids. The recent flurry of "gender" and "alfabet soup" propaganda pushed by the current US regime just adds fuel to this fire and has given Putin a plausible (if false) cover of being the one who "defends traditional Christian values", going so far as to offer "asylum" to those who want to "flee corrupted Western values" [1].
5 - This gives the kleptocrats in "the East" the excuse they needed to make a push for creating the "third Russian Empire" to keep out the "new Mongol Empire" while their counterparts in "the West" have all the excuse they need to expand NATO to keep the "Russian bear" at bay.
6 - rinse and repeat
[1] https://www.businessinsider.com/putin-russia-safe-haven-for-...
