>>52912396the more I think, the more it fits
Sturdy means they can't be OHKOd, meaning they can be relied on to get at least one hit in against even the strongest of foes, and makes them generally just more reliable defensively
they have access to multi-target moves like Rock Slide and Earthquake, and Bulldoze at least can be learned without even needing TM (Rock Slide also but only going off the PLA learnset, so probably not realistic), which I assume would be important since they're probably operating on a budget against more sophisticated foes. Smack Down is also useful for taking care of flying mons, and making them vulnerable to the mass-hitting Bulldoze.
Stealth Rock can make enemy reinforcements a bit easier to deal with (though likely won't ever trivialize them since Pokémon weak to Rock likely won't be used much against them)
SD/Explosion is a powerful last resort and not exactly unheard of among their type of group
Geodude doesn't evolve until level 25, but gets access to its final evolution immediately after, since they are a large organization they have no worries about finding another member to trade, having a bread-and-butter Pokémon thay requires this also would help build a sense of camaraderie among them
Of course, a bunch of Geodude spamming Bulldoze would probably do considerable damage to each other, so they'd probably want to get their hands on Rock Slide if they can manage, but a fierce blow at the enemy at the expense of collateral damage isn't a line they're unwilling to cross if necessary
The above factors as well as Geodude's relative abundance in its preferred habitats should make a convincing enough argument that this would absolutely be their main grunt-tier Pokémon
