I think he tried to move his arm position and fell forward. If you’re doing a TT and trying to put in a good time you’re going to be on the limit.
I can’t imagine running a disk, even my 40mm rims get buffeted some days.
When he hit that bump, the bars rotated downward, causing his balance to shift forward.
When I first watched it, it appeared the bars broke from the impact of the bump. Watching it on a phone makes it hard to tell though.