IME routines can change very suddenly. My DS dropped his nap over night. He was also very unhappy to have a nap capped (I did try for a while) and didn't recover until almost BT, it was awful. So we continued with a long nap (2hr) and short nights (10hr) as he was well rested...until one day he was ill, slept a 2.5hr nap and never napped again.
It could well be that your LO is ready to drop the nap (which avoids capping and dealing with the awful consequences)?
Or, if your routine was stable before the clock change, he could need a strong push to shift his body clock. You could try 30 min later to bed night, another 30 min the next night (don't let him make up for the lost sleep at nap time though), and that ought to force him to sleep past his body clock WU time and shift to the new time. After he's shifted his WU you can bring BT earlier again to increase the night length back to whatever his normal night is. I did this last year at a similar age, moved him 1.5hrs instead of 1hr, broke his body clock and then brought BT earlier to give him a full night.
Just a couple of ideas x