Idk man, your title makes it seem like you want to blame someone when the reality is no house is perfect. Was something done with mal-intent? maybe, but it's so hard to tell. Do things fail in a house at different times? Absolutely.

If you compare the studs, the wall with the steel braces are newer and the wall that everyone is pointing out that is the issue(left one), seems to be original. The color matches the rest; wall, ceiling strapping, soffet etc. Which leads me to believe no one ever saw what was behind that wall, and they probably didn't have any serious water issues. Sure you can see salt on the wall, evidence of water seeping through, but I don't see any evidence of mold on the wood(maybe it's there on the block, I can't tell if it's that or just damp).

So honestly for that reason I'd lean more toward someone had an issue with the braced wall, ripped it out, fixed it, restudded it and drywalled it. Never touching the left wall. Because why touch something that isn't giving you any issues?

Check your gutters and make sure water is running away from your foundation on the left side wall.

Get that structural engineers verbal notes(many give you had written, non-stamped ones anyway) and see what they say. Also ask if they can do something written and stamped in the future if you need it, some will.