OAKMONT, Pa. — When sheets of rain descended upon Oakmont on Sunday afternoon and an army of groundskeepers started taking squeegees and towels to the fairways, a tumultuous finish and bizarre turn became inevitable at this U.S. Open. The backward leaderboard movement did not stop all day at the venerable Pittsburgh major venue, and it ended with J.J. Spaun at the top — the man who survived a soaked and “borderline unplayable” golf course.It was the 34-year-old Los Angeles native who hit the 64-foot birdie putt of his life at the very last moment. The PGA Tour journeyman who collapsed under the pressure just a few months earlier at the Players Championship in the face of a blazing Rory McIlroy. The golfer who was making just his second start in the U.S. Open and came into Sunday with his first shot at a major championship. Spaun nearly ejected himself from the tournament with a front-nine 40, but he didn’t let it end there.Spaun began the day 3 under, one stroke behind the leader, and finished at 1 under, two shots better than the next best competitor. It took more than a back-nine 32 for Spaun to become the eighth first-time major winner to win at Oakmont in 10 U.S. Opens, though he did hit the shot of the tournament to that point at No. 17. His drive on the par 4 headed directly for the pin, nearly dropping in the cup. He converted a two-putt birdie to take the solo lead heading into the final hole, ahead of Robert MacIntyre.Oakmont’s par-4 18th stood between Spaun and his maiden major championship victory. He roasted a drive down the fairway and then a 6-iron that found the left side of the green. Suddenly, with playing partner Viktor Hovland’s ball sitting just a few feet behind his on the green, Spaun kneeled, shielded by his umbrella. A driving rain fell. He had the bonus of watching Hovland, who went first.Hovland gave it a run. His putt breezed by the cup on the low side of the hole.Spaun stepped up and it was clear that he learned. The putt tracked toward the hole and fell in. A miracle putt. A birdie that would change the course of his career. A moment that would define this U.S. Open at Oakmont.