He thought it was safer than it was.
But I don't think he thought it was close to a 0% chance of death.
It's clear that he knew it was somewhat risky.
It failed after like 25 dives which means around a ~4% failure rate.
I'd hope he thought it had less than a 1% failure rate.
Who knows what the true failure rate is. Maybe they got really lucky, and it actually had a higher failure rate. Maybe they got extra unlucky. Who knows.
I just can't fathom people would pay $250k for a miserable time and a decent shot at death.