So many news reports and experts interviewed say the hull was a composite material and not at all standard protocol design/engineering for those extensive sea depths.

The concept was innovative, but came with risks as each time it was submerged at those depths it became more vulnerable to the pressurization of those components used.

That was a private company and not regulated/approved by any of the known regulatory boards - worldwide!

Even Josh from the TV show; Expedition Unknown said 'NO' when he had the opportunity to travel aboard the Oceangate for the TV show. https://www.newsnationnow.com/travel/missing-titanic-tourist-submarine/expedition-unknown-josh-gates-titan-sub-safety/