I don’t know why he insisted on sticking with Carbon fiber when multiple tests over and over again the strands would snap during tests. There is a reason other deep water submersible use Titanium.
The Netflix documentary says that vessel big enough to have 5 people on board would have been far larger when made out of a more conventional material. This was another business-driven decision as they wanted to charge for rides and more people = more money.
Titanium was proven and well-known and established for the use. You can't be a disruptive innovator challenging the dogmatic establishment and trailblaze a new way to make money by being boring and doing what is well-known and established for the domain you are working in.
You have to defy all the voices telling you are wrong and its going to fail.
(Of course, most of the time those voices are right, so if it is something with lives on the line, you also should be making sure you have the resources to test it thoroughly so even if it isn't well-establlished and known before you start on it, it is well-established and known through your team's work before you start putting it in the position to kill people.)
The submersible would have been much heavier, hence would have required a much bigger ship, with bigger crane, to haul it, which is times more expensive.
