moving to garlemald or elsewhere

[Belhi]

The Sahagin summoned Leviathan because the people of Limsa denied them the space to build spawning grounds on the coasts. The Garleans had nothing to do with it. In fact many of the beast tribes were adamant on summoning their primals before the Garleans even stepped foot on Eorzean Soil.
Another example is the peace treaty between Limsa Lominsa and the Kobolds. This treaty was broken after Limsa Lominsa moved in over conflicts over their ore. I'm assuming some kobolds were killed as well since the dialogue that titan gives and the cutscene between Merwyb and Y'shtola imply it.

The reason that the Sahagin needed those spawning grounds that lead them into conflict with Limsa is because the Calamity, that was ultimately caused by Garlemald and the Meteor project, destroyed their old spawning grounds leaving them no where to hatch and raise their young.

Also we have only really seen the primals being summoned in the last 5 years or so. Garlemald first invaded Eorzea back when the battle of Silvertear Skies happened. Infact before that battle it was a lot harder to summon primals because the explosion at lake Silvertear flooded Eorzea with additional Aether.

[Gaiussenpai]

I'm sure it was lahaderpbra and his buddies that caused it since its always Ascians/allagans/aliens.

Speaking of that I hope Elidibus turns out to have interesting motives from his counterparts.