Its rent seeking because they’re using the government role to bring in the dough for themselves after they get the role. It just takes a bit of money upfront similar to a landlord buying a house. That’s also how you restrict government roles to the rich who only use it for personal gain. Similar to people who believe that Trump is generously by “donating” his salary back but not realizing that he and his family are earning far more in bribes and kickbacks using his position.
You're asserting a lot of things that aren't in the article. If you want to argue Victorian-era MPs were all motivated by corruption then go ahead but you'll need to cite strong evidence for that, because the general consensus was that MPs of that time were not particularly corrupt. As the article says, they didn't even spend much time on lawmaking at all, so there wasn't a lot of legislation to abuse.