I’d say most of the developers with a large number of apps are not developers but publishers. They are either publishing the same app again and again with different content (books, watches etc) or are the output of app generators. Either way, the functional ability of these apps is very low.
All this should give some encouragement to people thinking of developing apps. Although there are hundreds of thousands of apps, a large proportion of them have very little value. The market for good, functional apps isn’t as crowded as it might seem.