Zombiefied Piglins Overspawning at Portal

https://gyazo.com/40c22256a189c2dfadcd6fd20fe3f6bc

Apologies if this has already been posted I couldn't find one like this.

Basically Zombiefied Piglins are mass spawning at my overworld nether portal. When I went through the portal there were no zombiefied piglins in the nether.

How to recreate
1) Build a nether portal in the overworld
2) Wait.