I'd imagine there are a lot of people who aren't that clever who got in. When you look at the numbers from some public schools, it's crazy how many go to Oxbridge, but then that's what people are paying for. It's not just, take the exams, and hope for the best. If there's any chance you'll get in, then you'll have every advantage in preparation - guided to easier subjects, and easier colleges, prepped for interviews and exams, and with more insider information than someone from a school where just one or two a year apply.
I do think it's unfair on Liz Truss though. Looking at her education, it wouldn't surprise me if she was academically clever, and let's face it, she got to be Prime Minister, so clearly has some impressive political skills. I'd imagine most people would struggle to be seen as clever in the full glare of a political career. There's always an opposition, and millions of people who don't like you, because of the party you support, happy to mock whatever slip you make, or whenever something doesn't work out. If you get through a career without saying a couple of really stupid comments, then you're very lucky, as they'll follow you around for ever more.
I suspect many on here would come across as a bit odd too, if they were constantly having to talk about their opinions in the media :)