Bush never had to prove his wmd claim but Obama has to prove Usamah is dead, wtf?

I didn't like what Bush did, and i voted for Obama...but its clear to see that with a year to the elections this assination was just in time to give Obama a Boost in the polls..Its obvious now that Osama was not found living in between caves that Bush knew exactly where Osama was, but since the the Bin ladens were friends to the Bushs, He couldnt kill their son Osama...