Space feudalism actually makes a lot of sense.

When I first started reading the series I was dumbfounded by how humanity could go back to feudalism after spreading throughout the galaxy, but it actually makes total sense!

It'd be impossible for a centralized power to completely control every planet in the galaxy, even with FTL travel. The distances and the numbers are just too much for a hands-on approach. So having an emperor decide who rules over what piece of land and give them freedom as long as they pay tributes is the only practical way to rule a galactic empire.

It goes to show that technology and human politics don't need to evolve at the same pace (or in the same direction).