Samsung is the same at the lower end, with a plethora of A, M, and F series phones, many are overlapping each other.
The game in the lower end is to maintain customer's awareness at any point in the year, at least that's the theory. Thus Xiaomi and the whole BBK gang (Realme, Oppo, Vivo), are constantly releasing new phones, refreshing the previous models every 5 to 6 months. Most of them are basically the same phone, but with different cosmetics and newer Android version. Thus whenever someone goes into a store, they see "oh look, that's a new model, I'll get that."
At least that's the theory.
Both Xiaomi and Oppo are indeed trying to be premium (Mi 11 Ultra and Find X3 Pro, both are in the $1000 price range). But they forgot the software side. They're still in the mindset of being an ODM company. These companies are severely lacking in software support though, with majority of their phones get no or just one major Android upgrade. They're too focused in selling new phones and acquiring new customers.