Pets and villagers disappeared

My pets and villagers disappeared. I traded with my villagers, and traveled a few hundred blocks, then saved the game. I logged back on and came to check on them, then the villagers and my pets disappeared. Before the villagers disappeared, I put my villagers on boats for days straight. None of them were name tagged, and I play on a multiplayer server. I didn't put my pets on boats.  I have a gold farm that spawns a lot of zombie piglins, and the gold farm is near my villagers, but my gold farm wasn't turned on at that time. When my gold farm is turned on, a lot of lag happens. All of this is happening in the overworld. My simulation distance is 4 chunks. May I know why this is happening. Thank you!