It's a good point that providing the security systems of nuclear power plants is cheaper and more job creating than space datacenters. You can also get more uppity when international adversaries nuke your datacenter on US soil as opposed to space.

But more money to a guy that recycles $100m+ into politicians every election cycle, provides decision maker influence to subsidize space skynet. Continuity of nazi/zionazi ideology may require being beyond any temporary loss of control over law.

necessary ground-based necessities for space based data centers?

They could be configured such that no off switch exists, no manual administration is required, and it's a fully self-sovereign system that can only be shut down by sending a missile to space, and physically accessing it to extract the data or encryption keys it contains is even harder.

you can easily fortify and militarize your data center on earth to the extent that no protester will ever come close?

Only if your definition of "protester" excludes anyone using weaponized drones, but that misses the point. The current meta for fortifications right now clearly favors the attackers, and that's especially going to be true for a facility requiring large power inputs. That meta no longer applies if your data castle is in space.