At some point, though, boots on the ground matter more than words.
The Russians have evidently reached that point.
As best I can tell, this conflict was entirely, completely, utterly avoidable simply by Ukraine following the terms of the Minsk agreements[0], voted on unanimously by the UN (including Ukraine and Russia).
Why Ukraine chose not to live up to their written agreements is anyone's guess. In hindsight, it looks pretty stupid. It's almost like—when you don't live up to your word—people stop caring what you have to say.