I am Russian and nationalistic and I can tell you that there's enough low hanging fruits around Russia who are not in NATO. So weak EU might certainly lead to attemts at picking those fruit.
Why? There is no EU based military coordination. Trade war EU, shooting war NATO. Balance of power games like missile shields in border states are in NATO's purview.
I use "Weak EU" in the meaning of "dysfunctional states".
If and when a large subset of NATO states are dysfunctional, it will definitely create opportunities.
It's like with rot - rotten things don't stay put they spread rot around.
