Oh dear I'm sorry you had such a hard time.
Gosh, total nap refusal! Well done for getting him to bed early though and he did pretty well didn't he? I would have expected a lot of OT NWs based on having had only one nap!
So, it's a bit of a mystery. I'd be tempted to put down as some sort of blip and not think too much about it.
It's not totally unheard of for a LO to drop to one nap extremely early but it is very unusual.
What are your feelings on moving forward?
I wonder if capping the first nap would help to create a longer second A time to fit the second nap in? I didn't like to cap my DS's nap at all so it's not something I am really keen on myself but I don’t see how you can fit 2 naps in if he is UT after 3.5hrs second A time