Alright so.
When Bradley Williams steps up to hole 17 he is 2 strokes behind Gannon, but Gannon has not completed 18 yet. I don't have the timing exactly here, but in Bradley's mind maybe there is a chance Gannon could birdie or he could take a big number (lots of 6+). If Gannon birdies then Bradley can't catch up without a miraculous 400' throw-in for eagle on 18 or an ace on 17, if Gannon takes a big number then it makes Bradley's safe play very smart.
He decides to lay up on 17 and play aggressive on 18, he thinks he's more likely to take himself out of contention by bogeying 17 than he is to give himself the stroke(s) he needs by birdieing it.
This decision is debatable; we saw good players overturn their drives going for it and bogey, but we also saw people go for it and leak OB in c1 and take an easy par, theoretically he should be able to play for the safe miss and give himself a high chance of a par with an aggressive play. But he felt he was better off going for 18.
The rain starts picking up and by the time they get to hole 18s tee Gannon has finished with a bogey. Bradley Williams is now 1 stroke clear of Kyle and 1 stroke back of Gannon.
On 18s tee he plays aggressive but doesn't quite execute his shot, it looks a bit nose up, or not turned enough. He manages to stay inbounds but is quite far away and extremely unlikely to be able to get to the island. As he progresses down the fairway the rain becomes a monsoon, rain is so heavy that you can barely see 200' down the fairway, but he knows he needs a birdie to get to a playoff.
With no clear shot, Bradley lays up, probably hoping to give himself a 80-100' jumper, but he ends up 150' short.
By the time he gets to his lie Kyle has laid up 3 times and has a 90' jumper onto the island, it's likely he'll get a 5 and possible he'll get a 4. Calvin is on the island putting for 5 and should be a non-factor.
Bradley has 2 options; try a throw in or lay up again and play for 5. If he lays up he is pretty much guaranteed a 5 on the hole and barring a 90' jump putt make from Kyle (possible, but unlikely) he'll take solo 2nd place. If he tries a throw-in he has a small chance at birdie, small chance at par (doesn't go in but sticks the island) and most likely takes a 6.
The most likely scenario (Bradley takes 6, Kyle 5) means he gets T2nd, loses $293 and 2.5 tour points. He could also take a 6 and Kyle 4 and then he gets solo 3rd, loses $595 and 5 tour points. Remember that last year the difference between being qualified and in the play-ins for the DGPT finals was 3.04 points.
Of course, if he does make the throw-in he has a chance of getting an extra $1000 and 7.5 tour points.
Now, Bradley decided to lay up and Kyle ran his putt long and missed the comeback taking a 6.
I think you can argue with plenty of his decisions, but remember that he was trying to go for 18 on his drive, but due to a fluffed shot or the conditions affecting him he didn't get to where he needed to. His 2nd shot on 18 was a layup but probably hoping to give himself a look at a birdie still. His 3rd shot was probably a hard decision playing the odds, knowing he had a chance to lose $585 and 5 tour points, judging that to be more likely and important than the outside chance of gaining $1000 and 7.5 tour points (not to mention a win).
Personally, I think playing safe on 17 was probably a mistake, he could not have predicted the weather but it seems like a hole where birdie and par are much easier than on 18. I also think that the gain vs potential loss was big enough on his 3rd on 18 that he should've gone for it, but the conditions were terrrrible and I understand the choice.
Regardless, I think it's more nuanced than most people make it out to be.
