It’s a tragedy, but high risk activities are by definition going to have a few.
And if you tried to take paid passengers on a homebuilt uncertified aircraft today you would go to jail. This isn't the early days. The challenger deep was reached over 60 years ago. We've been building submarines longer than airplanes. We know how to do this stuff safely. This was negligence.
Or then you take things slow and you end up like NASA who has not launched any new rocket in years. Is that better?
Science, discovery, boldly going where no one has gone before? Absolutely safety is going to be somewhat compromised. Taking rich people to the gawk at the Titanic? I, personally, think you're a bit of dick for MacGyvering a vessel together and calling it good enough.
(Lesson learned the hard way)
It's probably the goal, but complex endeavors mean you need to iterate to get there
This is reckless and it is stupid and excusemaking for it has no moral grounds.
Excuse me, there are several companies operating submarines that visit the Titanic with tourists?
Submersibles visited the Challenger Deep in the 1960s. We know how to build them, we know how to build them effectively, and we know many of the ways not to build them. "But we added tourists!" is not a meaningful factor here unless what you meant-but-wouldn't-say is "but we value engineered it!" in which case: yes, exactly, that's what safety rules are designed to put guardrails around.