

Also, I’d guess the ideological base that kept monarchies around as a system (at least in Europe) has been shattered fundamentally.
The idea, that the ruling class is put there by god’s grace isn’t something that can work as the foundation of power structures in our post-modern world.
There’s a reason why the remaining monarchies in Europe are really democracies, that simply keep a bunch of monarchs around for representational purposes.
If there are no clues pointing to another motive, it’s the most likely explanation, thus they are investigating it as such. It’s not a confirmed femicide yet, though.