Nice camper by the way! Can't wait to see pics of the final painted shell.
Without doing an on-site forensic, did the legs lower onto a thick mat of long-leaf pine needles (I've slid badly on pine needles in the past)? If the jack's landing pads were lowered onto the teflon-like slippy needles on hard packed ground, they (one landing pad) could have just slipped out (like walking on ice), and caused a cascade of instability with the other pads/legs, and the weak point, the jack attachments, just let go one at a time (even well connected)....Just a thought....
For it not to have sustained major structural shell distortion/damage falling from (near full?) jack extension, that camper must be built like a brick. Looks like a keeper to me.