I seriously can't believe that a problem that has evaded mathematicians for decades could turn out to have a 9 page elementary proof! I don't know whether to b

I seriously can't believe that a problem that has evaded mathematicians for decades could turn out to have a 9 page elementary proof! I don't know whether to be excited that, maybe, other hard problems in mathematics could have such elementary proofs, or depressed that mathematicians took so long to solve a problem with such a simple answer :)