Why didn’t they?
They didn’t because they didn’t want to.
They could have given them the Chechen treatment, but it wasn’t worth the trouble.
In Ukraine, they are now holding on to the parts they really want.
They are not going to attack NATO; they know we could destroy them if we had to."
Maybe... and yet... somehow, we can't destroy Russia in Ukraine, can we?
So, you are understating both Russia's capabilities and their ambitions, not to mention their willingness to suffer massive casualties, as demonstrated since February 2022.
Further, you have not been listening to Russian government's propaganda to their own people lately.
They are absolutely revanchist, expansionist, imperialists -- to restore the old Soviet/Tsarist empires.
Of course, you are 100% entitled to keep your own head planted firmly in the sand, but that didn't work so well for the West during the 1930s, did it?