uh, is this logical in any manner

I just watched a pstars pro make what I thought was a pretty ridiculous fold.
step F 1 and 2nd pay 2100 ticket, 3rd pays retry @ 700$

stacks
btn :7500
sb : 2500
hero : 3500

BTN opens to 450 @ 75-150, hero tanks makes it 1800!, btn tanks for about 40 seconds and shoves, hero folds pretty quickly.

I am so lost here. Mainly why hero is 3bing so large if he intends to fold.

On the face of it, it looks like a pretty strange move. Maybe it's got something to do with a) table image and b) payout structure.