Moisture issue/floor buckling

Looking for some insight on what might have caused this floor buckling and subfloor rot. The crawlspace pictures are directly below the buckle.

I'm not well versed in moisture control but my current theory is the holes in the ductwork going up into wall (zoom on last picture) forced air between the subfloor and the hardwood causing moisture to get trapped?

My current plan is to cut out the bad plywood, hardwood and replace with new plywood till level, then put my lvp back and replace that entire duct leg to the register.

Any insight or recommendations would be helpful.

https://imgur.com/a/XJ1fv5k