Because it's not HIS idea, it's an idea that he read from people smarter than him.
You've brought up a good point that I'll provide some follow-up evidence/elaboration on. Because he (allegedly) has read thousands of books on a ton of subjects, he's very good at regurgitating information from these authors but his own thinking abilities are downright horrendous. The reason I think most people believe he is smart is because he can use arguments made by other people and knows a lot of random obscure knowledge, but he (self-admittedly) said that he's not very intelligent, and when you listen in depth to his videos or tweets he constantly uses terrible logic or contradicts himself. Almost every video he makes is filled to the brim with personal anecdotes that he uses as evidence, using them often far more than actual statistical evidence, alongside making appeals to how because some expert/book said it, it's therefore true.
For example, in "Hanging Out w/ Rudyard from WhatIfAltHist | 315b" from the Sitch & Adam Show, he mentioned that race is real, and when asked to elaborate, he says that experts believe in it, his friends who are experts believe in it, and books say it so it's true.
Which is completely contradicted by a tweet he made where he gets mad that people ask for actual evidence instead of just trusting his 'obvious' conclusion from a random book, going on to say that authorities aren't trustworthy. (which is not even to get into the rabbithole of how much Rudyard hates empirical evidence in general)
These are only a few examples that I could remember off the top of my head. For every time he repeats some correct point someone else has made about academia, conservatism, history, etc. there are just as many times he says some insane nonsense like how the eucharist in the catholic church was a psychedelic, ancient Rome was atheist, people have definitively proven magical powers, etc. I've had the displeasure of watching a significant amount of his content, and the more you listen to him the more you realize how everything he says (other than points he lifts from smarter people) is complete insane gibberish.