It's easy to second guess after the fact. I don't think they did anything terribly stupid, but it sure didn't go well.

Having hiked in similar terrain, and having experienced a flash flood personally near Ojai, California (where this occurred), I know just how dangerous those canyons can be. Those canyons have an established reputation for being killers. In the video the leader said that there was wood in the camp area "four feet high" from a prior flash flood. I wouldn't have stayed in the camp area either. In retrospect, probably moving to higher ground nearby with their gear and hunkering down would have been the right thing to do, but I can understand why they'd abandon their heavy gear and make a dash for the nearby trail head. If I were to criticize their decisions, I might find fault with them waiting so long to bug out.

Then, having bugged out, when the water rose quickly, they were essentially screwed when high water stopped them. They couldn't go forward; they couldn't go back, and, soaked to the bone and their gear abandoned, they didn't have the capability to hunker down. Keeping on the move wasn't such a bad idea. If you look at the video, they actually did a good job on navigation. They came out very near the trailhead. But there was a cliff that didn't show on the topo. They were truly stuck. I might very well have made the same decision myself.

The one observation I will make is that playing "beat the storm" is seldom a good idea. If there's a storm that looks like trouble moving into the area, sometimes the best thing to do is postpone one's trip. I've seen more than once people who assumed they'd be out before the storm and then either they were delayed or the storm moved in more quickly than expected, and they got into trouble. One person I know of died in just such a scenario, and another, a friend of mine, came very close.

I frequently make "alpine starts" (super early, pre-dawn starts) on my hiking trips. It's a real temptation to check the weather the night before and then sleep in as much as possible, jumping off at the last possible moment. This story is a good cautionary tale. It's worth it to get up that extra few minutes early and check that weather report.

HJ