> why haven't we seen mass death from repeated 35℃ breaches?
Because we haven't seen very many 35℃ wet bulb temperature breaches yet. The nominal air temperature is much higher than that all the time around the world, but it's only when there is very high humidity at that temp that humans start to overheat.
IIRC there have only been a few instances so far where the web bulb temp limit has been breached, e.g. some instances around the Persian Gulf, and maybe also in Mexico near the Gulf of California (not sure about the latter if it's even been breached yet, but I know it's at risk).
Because we haven't seen very many 35℃ wet bulb temperature breaches yet. The nominal air temperature is much higher than that all the time around the world, but it's only when there is very high humidity at that temp that humans start to overheat.
IIRC there have only been a few instances so far where the web bulb temp limit has been breached, e.g. some instances around the Persian Gulf, and maybe also in Mexico near the Gulf of California (not sure about the latter if it's even been breached yet, but I know it's at risk).
Edit: Wikipedia page has a list, https://en.wikipedia.org/wiki/Wet-bulb_temperature#Highest_r.... There have only been 10 recorded instances where wet bulb temp exceeded 35C.