T16 over run map spawns with next to nothing in it?

Not sure what I just did but I crafted a T16 map juiced for rarity and abyss. Should've been mayhem. Instead it spawned maybe 3 abyss fissures and nothing else. The Abyss fissures had mobs but the entire rest of the map was devoid of mobs except of the boss.

Kept a video of the whole thing. I'm assuming I used something that contradicted something else and caused this and it's not a bug but I've got 1500+ hours in game so far and haven't seen a map like this before. Was just a regular map, not a hideout or anything.