If jesus died for our sins, but jesus was only born 2000 years ago, what happened to people before that?

Edit: Okay, im really concerned that the answer is so that sacrafice was not the way to atone anymore. Jesus's death is so crucial to Christianity, I genuinely dont understand how this is the answer. If you applied this to a human, they'd obviously be considered a psychopath

Christianity makes game of thrones seem tame! At least George RR Martin tried to make it make sense. Please someone help me understand! I know loads of redditors are Christian