Their mindset is: the upside is likely so, so, so immense, and the probability of amazing outcomes is so much higher than the probability of catastrophic outcomes, that the gamble is worth it, and it is not in fact a pure gamble because they can (in theory) try really hard to build it really slowly and carefully.

So even with their earnest belief that there is a > 5% chance this technology could be 1) capable of autonomously killing billions of people during this century and 2) may not be sufficiently aligned and might actually act on that capability, the EV basically still sums positive, to them.

Not saying this is necessarily a good or moral calculus. But it is what they think. There is no conspiracy or plot or deception.