I guess the reason he was talking about it being "bad luck" was he was dropping every putt from almost any where for 3 days. That is why he was in the lead in the first place. He switched to that belly putter the week before and he has been dropping them. Then on Sunday they just would not fall for him. I am sure it had something to do with pressire but he will never say so.
I thought the biggest mistake he made was pulling out the driver on the last 4 or 5 holes on the front nine. The front nine is where you want to make your birdies on that course and he had been hitting irons all week and making plenty of birdies but when he pulled out the driver, which he does not hit that far, he was playing from the ruff more and had longer putts and fewer birdie putts. If he had be playing from the fairway on those holes instead of the ruff he would have had birdie putts instead of par putts and he would not have made so many bogeys ion those holes which would have given him a large lead on the back nine.
He made one bogey on the front nine for the first 3 days and he made 3 bogeys on the front nine in the last round. Yes he was missing putts but they were longer putts and they were for par saves more often than for birdie and that had to do with his tee shot which was bad most of the day sunday.
He changed his game plan and he lost because of it