Well, first off, you're in the wrong thread. Your points are valid: the viewport glass was technically rated for the depth, but the viewport company said that they wouldn't actually stand behind it because OceanGate was using a different hull. The viewport company suggested a different viewport but it was more expensive and OceanGate refused.

The torque on the bolts wasn't something that had occurred to me and is interesting.

My theory is that the carbon fiber hull collapsed, due to the strain of pressure cycling. It's something the whistleblower was concerned about, and apparently they accepted visibly flawed carbon fiber for the hull. You can read more here: https://techcrunch.com/2023/06/20/a-whistleblower-raised-safety-concerns-about-oceangates-submersible-in-2018-then-he-was-fired/