Further research shows that they blew everything up trying to deal with the ancient, insatiable, worms they released on themselves out of curiosity. Upon reflection, it is probably better that we didn’t arrive earlier.
Alien #1: … HEY KORG! … look at this! … (picks up human skull and starts comically operating the jawbone) … HEY LOOK AT ME! Imma intelligent species and my economy is more important because I have to pay for these worms … so imma gonna blow up the world for some reason
KORG: … Stop messing around Kang … this place gives me the creeps, let’s get out of here.