Raw Power
Ves and the living gem implicitly cooperated with each other because they were heading in the same direction. The soldiers in their way impeded both their progress, so Ves did not mind the fact that the gem unleashed the cyclopes on them in order to clear he way.
Yet now that their paths diverged at the final stretch, those giant beasts were no longer on his side!
He had no doubt that if he attempted to screw the living gem over, the humanoid monsters would crush him and his Larkinsons the same way they crushed all of those poor infantrymen!
Ves had no way of fighting back against the might of these terrible experimental monstrosities. He was cut off from his airfleet and didn't have any of his powerful mechs and mech pilots by his side.
Though he thought highly of the combat prowess of his honor guard, they were never meant to fight against mechs or giants who approached the size and combat power of an actual mech!