My wife, I, and several people I know had iPhone 12 or 13 Mini. Their battery life was pretty terrible and word soon got out it was. I think this was in the end what killed it for people who are normally buying Apple flagships and were considering a Mini. It was very hard to get through the day with a Mini.
Besides the abysmal battery life, I think the market for small phones is maybe simply not there. Samsung keeps around one smaller model (base S-series) and arguably the Z Flip is a smaller model (but persistent hardware issues). If there was a large demand for flagship-class small phones, I am sure some Android manufacturers would make them.
My hypothesis about the supposed non-existence of the small phone buyer is that they very much do exist (personally, haven't bought anything other than whatever was the smallest Xperia at the time in more than a decade), but that this group has little overlap with the group willing to buy for list price on release day. But the perception of success of a given phone is very much dominated by the latter, the long tail of buyers isn't really seen. Even if the release day premium over mid-lifecycle street price (in countries where price fixing is not allowed) goes to the retailer and is of very little interest to the manufacturer.
Manufacturers should just move compacts to a three year cycle and forget everything about hyper-optimizing desirability for the kind of buyer who spends too much time reading questionable review sites.