It targets people that have plenty of cash for a flagship but are willing to forego the top tier specs for a smaller size. Apple prefers you just buy the pro. And if you don't have much cash you can get the reheated 2017 iphone 8 with SE slapped on it :)
I bet if they made a mini T the price of an SE with a more limited camera and screen spec than the current mini it would take 50% of SE sales away.
You can't judge the market viability of one aspect based on a single model.