It's a hormonal change, and happens at different ages. My daughter was dry on a night before being potty trained
They’re not ready to go nappy free at nighttime if they’re waking up wet AND that’s NORMAL and COMMON! Nighttime dryness is hormonal and can’t be trained. And unless things have changed recently the nhs don’t intervene until at least age 5 some times age 7 because it is common for bed wetting to be present :) Don’t stress it!
You can’t train a child to be dry at night. It’s all to do with chemicals in their brain. They’ll do it in their own time but can take a while. my 2021 son is dry at night but my 2020 isn’t yet and his nappy is still soaked in morning x