Viktor Hovland secured his fourth PGA title after he carded a final round of 66.
The Norwegian stormed from the chasing pack after Morikawa surrendered a five shot over night lead.
Hovland finished on 18 under after he carded two eagles, five birdies and three bogeys, which seen him come back from six shots of the lead at the start of play on Sunday.
The chaotic final round was epitomised by Morikawa’s round of 76 that consisted of two double bogeys on holes four and six.
Morikawa’s fellow American, Scottie Scheffler, finished in second place at 17 under after he matched Hovland with a round of 66.
The British contingent of Rose and Hatton both finished for a tie for ninth a 11 under par, as fellow compatriot Fitzpatrick finished one shot back in a tie for 12th.
In a final round full of twists and turns perhaps the most bizarre incident when both Stenson and Speith had thought they’d tee’d off from the ninth tee but was quickly shown to be the seventeenth.
Both players received a two shot penalty after the ninth tee had been moved overnight.