It’s pretty clear at this point the Emperor can do pretty much whatever he wants. He could have installed puppets in the Senate. He could have continued to dominate it and made an ongoing token effort to deal with their bullshit (which is really what government is all about and why conquering the world isn’t as fun or sexy as it sounds). He could have installed some sort of other system or infrastructure to support, you know, a galactic empire. One person, even with Dark Side force powers, can’t rule too many people at once. He can maybe manage a team of 20-100 people, and that’s assuming he has some small degree of magical mind control at his disposal….
So, the Emperor and Tarkin focus on making one really huge, high-impact investment: The Death Star. They throw in Alderaan as part of that investment. This doomsday weapon will supposedly free up their resources to spend less on administration, personnel and infrastructure, and continue to function without a Senate. It seems like a big investment until you realize how much they save by not actually having a functioning government.
This sounds vaguely Republican to me.