Climate warming, far right rising, democracy eroding, huges setbacks un humain rights, hate crimes exploding, biodiversity dying, activism more ans more criminalized, etc...it seem society is living its last moments, and doomerism looks like the only rational option. So what prevent you from being a doomer despite all of this ?
Even if I wasn't an absurdist at a universal atheistic level, it'd be hard to be a communist without being an absurdist at the societal level Camus is writing at. Trench warfare and line go up and electoralism are absurd things which drive you crazy enough to believe in them if you can't admit how arbitrary and meaningless they are. When you break from that idealism, Camus has the right confrontational framework for what comes next.