This just goes to show that deep sea exploration should be done by professionals, not rich people with a dream. I won't make jokes because no doubt their families are devastated.

Well this wasn't the first time a vessel has visited the Titanic. Nor was it the Titan's first time going to the Titanic. It wasn't even OceanGate's first dive on the Titanic. Titan had already been at least 13 times before and had been on more than one test dive to similar depths (it had 50 test dives but I do not know how many were at what depths).

It doesn't say so much about requiring "professionals" more than it says that anything in the deep sea is very dangerous. More dangerous than space, even. In space they have to worry about radiation, keeping pressure inside the vessel, and surviving re-entry. But they aren't concerned about building something that can withstand 400 times the normal pressure of Earth's atmosphere, they just have to maintain 1 atmosphere. But keeping 400 out is what is required for vessels that visit the Titanic.

Titan was designed for 450 times Earth's atmosphere, which meant it needed only a 4.5 inch thick hull, but it was actually built with a 5 inch thick hull, adding an extra half inch. While each dive would make the vessel slightly weaker than before, it is understandable to think it should last longer than its original use limit if it is overdesigned for the depth.

Even if everything was perfect, and the vessel was brand new, and even if OceanGate had 1000 backup plans, this still could have happened. The ocean is a dangerous place. Its sad that people lost their lives, but at least at that depth their deaths were instantaneous and painless in an implosion. At the same time, they knew the risks and signed the waiver. Overall a really sad situation for the family members remaining.