I assumed Tweedle studied there, too, but I wouldn't go so far as to call him "profoundly stupid." It's just that he's not as exceptionally intelligent as people like Seffie, or Gil, or Tarvek, or the MoP. Of course, whenever his schemes required exceptional intelligence to pull them off, he was still going to have problems.
One thing about Tweedle that has always impressed me is how quickly he recovers from his mistakes. I'm particularly impressed with his willingness to accept his mistakes and learn from them. That actually shows a quite a bit of wisdom. Granted, not making the mistakes in the first place would be even better.