I loved the 12 Mini, but battery life was one of the reasons to upgrade. 44% after 24 hours is very impressive. I often wouldn't make it through the day.
In my own experience iPhones somehow just love eating through battery doing nothing. I know because I have an iPhone I hardly use. It takes around 3 days to completely drain the battery doing nothing laying on my desk. Airplane mode does extend it by a lot. Android is much better at this, probably thanks to the "doze mode".