Ignorance and overconfidence in one self can lead to decisions that puts one in danger. If he didn’t understand the risks, overestimeted his control over the situation (as very rich people are prone to do) or simply surrounded himself with too many yes-men, then hi might not have thought he put himself in as much danger as he did. On the other hand he could also just see himself as an explorer and seeking rhe thrill as many of the dead bodies on Everest once did.

I’m sure there are many reasons he could have gone into that sub despite having been told the risk. I of course can’t know for sure, but it does seem more likely in light of his comment than without it.