For the same reasons that Hollywood makes 150 million dollar cast of stars blockbusters that tank on opening night because they’re so awful. It’s called covering your ass.
They producer tells his investiors and bosses, “Hey. I put together a great package with tops stars and a billboard director. What more could I do?”
Oh, I dunno. Check to see if the movie itself isn’t repulsively, stupidly horrible?
Same with HR departments: “Hey, the guy had a degree degree in Critical Race Theory from Harvard, and his interview was wonderful. What more could I do?”
Well, you could understand that the skills needed to get credentials, and the skills involved in giving a good interview (which are basically, in both cases, the skills needed to run a good con) don’t predict future performance in any meaningful way.