The brilliance of the ESP devices is not needing anything not included on a basic dev board for a huge raft of applications. The peripheral design is positively wonky, but they do just work.

Making the reference design into a fully usable product in its own right at a very competitive price, gives Espressif a massive advantage over its real competitors. Espressif isn't really in the same market as Arduino, they just happened to intersect.

Arduino is an education and hobby electronics brand. Espressif is a chipset vendor that made its reference design board so complete, cheap and flexible it became valuable as a product on its own. Other chipset vendors sell reference design boards for development, with the expectation that you will change it and produce it yourself to fit your needs. Espressif operate the same way, but if the dev board fit your needs, you don't need to produce squat; you just ship.

Espressif is a massive time saver in product design. Before the first cirquitboard has left the prototype factory, it i already proven to work with a bunch of hardware because you could strap up a bunch of dev boards with a cookie platter of interfaces and prototype from day one, bought from a hobby electronics shop with 1 day shipping.