Just like brilliant people that gets rejected from prestigious universities and companies, there's bound to be undeserving people that gets in.
Even if there's a vetting accuracy of 99.9% (for the sake of argument), there's still a chance that some lemon will fall through the cracks. So after 1000 seeds, there should be 1 lemon.
Now does that make the program any less prestigious? No, but these things happen.