Like the video [1] mentions, they were only improvising on things (including the controller) that would not pose a safety hazard if they failed. The critical components like the capsule were designed alongside NASA and others. People aren't just tossing safety to the wind, but trying to create a better balance. NASA does spend a extreme amount of money on compliance and safety - yet that doesn't prevent them from doing things like blowing up $600 million Mars probes because of a mismatch between Imperial and Metric units. [2]

Basically you cannot, no matter how much money you spend, prevent every possible mistake, or even every "obvious" mistake, because "obvious" is often only obvious in hindsight. And going too far on the side of risk avoidance leaves you frozen in time, unable to progress, even as you continue to make mistakes - which drives you even further into extremes of risk avoidance. Of course on the other end being completely cavalier about safety leaves you making mistakes you both can and should have foreseen.

So I suppose we'll just get to see which this was. If anything my prediction here would be that they started becoming so comfortable with these dives that they impacted the Titanic, going for that epic view, resulting in a cascade of system failures or even a breach, bearing in mind you're already going to be near critical pressure thresholds. Absolutely zero basis for my prediction, but I think it's much more probable than a controller failure. They had redundancies on the controllers, and could surface without them. But human hubris has no such constraints.

[1] - https://youtu.be/29co_Hksk6o?t=213

[2] - https://en.wikipedia.org/wiki/Mars_Climate_Orbiter