If you want to demilitarize a country you can do it by treaty, or you can do it by fact. Germany was demilitarized after WWI, but it retained the ability to build a large military and eventually did so.
The Russian view is that Ukraine needs to be demilitarized, de-Nazified and made neutral, it will otherwise remain a threat to them.
The demilitarization strategy is fairly simple: kill or disable everyone who can and will fight. This has been a grinding war, but at almost every stage Russia has had air, drone and artillery supremacy. It has taken great care to disperse attacking troops and to keep its own casualties down.
