Issue resolved, not a bug just something I didnt know

Created a new world and selected a seed based off a world I had previously tried on floating islands. Dug a cave and got set up, then, stone sword in hand started looking around. Up the hill to the right of spawn I got killed by a zombie piglin complete with his little gold sword. Found a ruined portal in the other direction over a river but cannot find a active portal or any other mobs to indicate there is a active nether portal ready nearby. Not sure why this dude was here. world seed 81304820086826180. Went back and killed him as the noise he was making was awful. Recreated world to see if it would duplicate and so far no although I am unsure how long I spent hollowing out the mountain prior to exploring and finding this dude.