Also doomerism, but I'd argue that a prominent figure that might fit this nihilism bill is / are Elon Musk and similar technocrats / futurists who strongly beli

Also doomerism, but I'd argue that a prominent figure that might fit this nihilism bill is / are Elon Musk and similar technocrats / futurists who strongly believe in Roko's Basilisk (https://en.wikipedia.org/wiki/Roko%27s_basilisk https://en.wikipedia.org/wiki/Roko%27s_basilisk), that is, to paraphrase, "the world is doomed, AI will rise, become our God, and exterminate humankind, but we have to ensure it actually emerges so maybe they will be merciful to us". Which I believe (but I'm no philosopher) is both nihilistic, fatalistic and religious thinking. To the point where I wouldn't be surprised if these people have or would kill people if they aren't in line with their agendas. They have the connections, power and money.