I do not know if what happened is possible in vanilla Minecraft, or if it's just a bug. I was playing in Minecraft world (seed listed below) with my friend on multiplayer, and I was going to a village to start a raid. I went to a pillager outpost nearby to get Bad Omens, but when I saw the outpost, pillagers continuously spawned. It spawned so many pillagers that they were literally pouring out of the tower. My friend and I were extremely confused, since we had never seen a pillager outpost spawn this many pillagers. We fought and killed most of the pillagers, but we almost died many times due to the sheer amount of pillagers that were surrounding us. Based on experience, I notice that pillager outposts spawn with one captain, and 8-10 pillagers. However, I saw 10 (possibly more) pillager captains, and saw quite possible over 100 pillagers. The coordinates to the structures are listed below so that you can see for yourself and maybe try to replicate the issue, but I have never seen anything like this. If this is a bug, it would be great if you could fix this, or if it is in fact possible for 100+ pillagers to spawn in an outpost, I suggest you remove it, since it caused my iPad to lag a LOT.

Seed: 749419307

Structure coordinates (x, z):
Plains village: 568, -840
Pillager outpost: 840, -904