It seems to me that interfering in a foreign election should be understood to be grounds for war.
Yes, and the EU, due to this fragmentation, seems to be a fertile playground for all this unacceptable interference by foreign powers.

That’s true but that fragmentation is also what limits the propagation of fractures. You can see it like sandboxing.

A deal with foreign intelligence is a dead with the devil that comes with a lifetime of subservience. And subservience to foreign powers is a greater evil than yo usual internal corruption. At least the locally corrupt in a democracy have some interest in things going somewhat well in their country. The foreign actors only care about theirs.