Oceangate had been warned by pretty much anyone with any knowledge of their efforts. They fired and sued their Director of Marine Ops who tried for stricter safety measures. They've already had to repair stress damage to the hull before the final dive. They were using parts not expected to hold up to 4000m dives, they were using flammable materials inside the sub.

The Thai team did something generally recognized as safe, and got caught up in a bad situation. The Oceangate folks did something that they'd been warned against repeatedly and consistently, something nobody thought was safe. Oceangate took every opportunity to do the wrong thing and try to profit off of it.

Insofar as wealth has anything to do with it, pedo guy happens to be pretty damn wealthy (ex financial broker). If those Thai kids hadn't caught a rich guy's attention their misadventure would've been a mere footnote.