Toilet rolls
The Alliance wielded toilet rolls as grenades against the Skibidis. How was that possible in-universe? It's possible they were actual grenades made to look like toilet rolls. But what if wielding a toilet roll against a Skibidi is more like wielding a cross against a vampire? It's not the cross itself that hurts the vampire; it's the faith of the bearer. The existence of Saint Skibidi Toilet implies that Skibs have some sort of faith. Can we weave something with those ideas?
Maybe this is more like what happens with the Orks in Warhammer. (I've never played any of it; I just know bits of the lore through cultural diffusion.) The Orks are telekinetic reality-editors, but they're too stupid to realise it. They just know that if they paint their spaceships red, they go faster. And it works, because the Orks think it will work. On the flip side, it means you can kill an Ork by pretending to shoot at them and shouting 'bang'. They think you've shot them, so they've been shot. And they die. Maybe Skibidis think the toilet rolls will damage them, so they do.