You could post a photocopy of a $5m signed cheque from a Qatari sheikh to Sepp Blatter on here and people wouldn't accept it, so it makes the idea of trying to prove bribery wasn't part of the bid pretty pointless.
Qatar have lots of money (and not the strongest bid on paper, that's untrue, its an interesting and ambitious bid but not the strongest, even FIFA reported so a fortnight ago), more than the other competitors, FIFA likes lots of money, Qatar won the bid. Make of that what you will.