Since 1980 Russia is lagging behind US in every military (and not only) aspect. They almost stopped new R&D due to lack of money. They were behind even before that but at least had the East Europe allies and lots of hardware. That hardware (even with some good designs that are still relevant) now in general is obsolete and mostly decommissioned.
Now they feel threatened. Not having the latest technologies ($$$) and with missile interceptors on the border they feel weak and bullied. East Europe countries are gone, now Ukraine previous ally is an enemy. On Asian front is same issue with Azerbaijan and Georgia. Can we blame US influence and politics about all this shifts away from Russia's influence zone ?!
Russia is just trying to catch up and have some influence and protect his own identity and interests. They do not want to be a satellite state. Example been EU with money and technologies , but so hopeless on any political and military aspect. Someone can blame GB been US Trojan horse for EU and blocking any decisions not approved by US. Let see if Brexit will change anything for EU.
It won’t be the first time country looks for own interest than to obey treaty.