The Wildcats squandered a 16-point halftime lead, completing their collapse when Wayns threw away an inbound pass with 22.8 seconds left that Crater converted into a go-ahead layup.
Wayns looked as though he might redeem himself when he was fouled by South Florida's Toarlyn Fitzpatrick on his own drive to the basket moments later. The sophomore made both foul shots to give Villanova a 69-68 lead with 11.6 seconds remaining in the game.
Too much time, it turned out.
Crater took the inbounds pass and went coast to coast, slipping by a confused Villanova defense for a virtually uncontested layup - and the biggest win for South Florida in a while.
Shaun Noriega hit six 3s and scored 22 points to lead the 15th-seeded Bulls (10-22), who had lost eight of their last nine but still advanced to play No. 7 seed Cincinnati in the second round Wednesday night. South Florida's only win over that stretch came at lowly DePaul.
Augustus Gilchrist added 16 points and Jawanza Poland had 11 for the Bulls, who won only their second Big East tournament game since joining the league.
Wayns finished with 24 points for the Wildcats (21-11), who at one time were considered national title contenders but instead will limp into the NCAA tournament having lost five straight games. They haven't won since beating DePaul in overtime on Feb. 19.
Just about the only bright spot for Villanova was the return of shooting guard Corey Stokes, who was questionable with a left hamstring injury he sustained in practice March 3.
Stokes didn't start the game but checked in almost immediately, hitting a pair of quick 3s and appearing to move well. He had 16 points as the Wildcats closed the first half on a 28-7 run to build a seemingly insurmountable 49-33 lead - but he didn't score in the second half.
The Wildcats have certainly been a banged-up bunch this season, with leading scorer Corey Fisher - who had 15 points against South Florida - dealing with severe tendinitis in his right knee, and Wayns suffering from back spasms only a few weeks ago.
Nova can add forward Mouphtaou Yarou to the list.
The big man went up to block a shot late in the first half and slammed hard to the floor under the South Florida basket. He didn't move for several minutes as coach Jay Wright a trainer check on him, then helped him back to the locker room. He reappeared on the bench a couple minutes into the second half with stitches to his cheek and ice wrapped around his ribs.
Villanova certainly could have used him inside in the closing minutes.
The Wildcats went the last 8 minutes of the game without a field goal, and yet nearly held off the feverish South Florida rally by converting 22 of 24 free throws.
The two misses were costly, though.
Wayns clanked the front end of a 1-and-1 with 48 seconds remaining and Stokes missed the front end of a 1-and-1 situation nine seconds later, either of which would have given Villanova some breathing room.
Much needed, as it turned out.