So we know Gorn capture other species, pit them against the Gorn and each other ala the strongest M&M copypasta, and then send the strongest M&M back to ~~M&M Mars~~ space. La'an was the strongest M&M, for example.
Maybe, originally on the Gorn home planet, the strongest just keep growing to fend off an ever increasing wave of hostile baby Gorn, becoming more cunning and intelligent on each subsequent generation. Maybe the spacefaring stuff was originally some Gorn thinking "wow this planet sucks, I need to get away from it so I'm not eaten by my own young."
And now, perhaps the Gorn do the same for their terrible cannibal babies - they get pitted against each other in the Baby Gorn Fighting Arena, Sponsored by M&M Mars, and the strongest are kept to become adult Gorn and to be used for breeding purposes and also for spacefaring stuff.
Maybe the Gorn are just trying to help other species become stronger. They are helping to select for the strongest M&M to send back to the factory for breeding purposes, and we just don't understand - cultural differences and all that.