zombie pigmen are insane, will not de-aggro regardless

I killed a zombie pigman about 54 days ago in game, and died hundreds of times trying to get my stuff back, but every time I killed all the pigmen, more would spawn, all still hostile. it got to the point that when I would walk through the portal, I would lag from the LITERALLY HUNDREDS of pigmen that were surrounding the portal, and die before I could take a step. fast forward to today. I go into the nether with all my gear, planning of farming some ghasts, and the pigmen are still there. I ran thousands of blocks from the portal, came back a long time later, and they are still hostile. this is absurd.