I'm 47 yrs old used to race so have some miles in, that being said.

Alot of what I do is instinctive for that moment.
When i hit hard bumps etc i lift my ass slightly off the saddle,always try to be loose as a goose.
Never think crash,if you have it your mind your already screwed.
You must of jammed the front brake hard to flip over(like you said)
I was decending a couple of weeks ago with a buddy we hit over 75km an hr on a 3km decent,never did it cross my mind that this was dangerous,if it did i shouldnt be on the bike.