There were two delays at the Robert Trent Jones Golf Club as rain impacted the final round.
However, when play resumed Niemann stormed into the lead to edge out Lahiri and McDowell, who had led before the second rain delay.
After starting with six straight pars, McDowell chipped in for birdie at the par-four seventh and followed that with two more gains before heavy rain halted play for 40 minutes.
Following the restart, four-time Ryder Cup player McDowell drained a 20-foot putt for a birdie three at the 12th to take a one-shot lead before the second weather delay came while he was playing the 14th.
While Smash golfer McDowell, whose last win came at the Saudi Invitational on the DP World Tour in 2020, picked up a further birdie on the 17th it was not enough to hold off the charging Niemann.
Niemann reeled off four consecutive birdies from the 14th to 17th to hold a one-stroke lead heading into the final hole, which he parred to secure victory.
It was a fourth win of the season for the 26-year-old, who also triumphed in Adelaide, Singapore and Mexico City.
Lahiri, who held a two-shot lead heading into the final round, and a solid performance from captain DeChambeau secured a second consecutive teams’ win for Crushers GC.
After moving into contention by the second rain delay with five birdies, six-time major winner Phil Mickelson found water at the par-five 14th and could not recover despite two birdies in the final two holes.
