HBO Chernobyl makes it very clear that the 3 men survived for many years after the accident and that at the time the show was made 2 were still alive.

https://www.youtube.com/watch?v=OHrVlyU3suk&t=132s

Edit: Everyone at the time probably thought that they were being sent to their deaths so they were staggeringly brave - but that's not how things turned out.