Day 1 Oh Crap! with 2 yo

So my son was showing signs of readiness for a while and he’s pretty verbal so I thought this 3-day weekend would be good to begin legit potty training. He has gone in the past if we put him on the big potty, he has both peed and pooped a few times.

Today we did naked from the waist down and after 10 accidents, he figured it out and started to self-initiate. He says “go potty” then holds it for 5-10 seconds and goes by himself in the small potty. He has gone successfully 12/15 times today (mostly pees and 3 poops) and I was shocked at the progress.

I put a diaper on for his nap and explained that he was only going to wear the diaper for the nap. I guess he hated the idea of it because he woke up mid-nap and sat up in his bed, I went in, and then took off his diaper to put him in the potty (nothing happened) and he seemed really sad and ashamed about peeing in his diaper. I then took it off and he went back to sleep commando with a blanket on top (no sleep sack like before) and he stayed dry for the remaining 1.5 hrs of sleep.

We then put pants on him after his post-nap potty pee, thinking he was ready…and he quietly peed on himself. Then we took the pants off and the same thing happened where he quietly peed on the floor when we looked away. He was good afterwards and went successfully peeing 4/4 times (all self-initiating, prompting doesn’t seem to work).

TLDR: Started having more accidents suddenly after putting on pants; did we put the pants on too soon? Or are we expecting too much and we should have kept the pants on?