According to Xiaomi's CEO, it is a heavily modified Android and Vela (Xiaomi's IoT OS based on the open source embedded OS Nuttx) to replace MIUI in all Xiaomi mobile, auto, and intelligent home products.
The only downside in chinies product is that they've the ability to copy & mass produce. But they don't have a plan to compete & sustainability for long-term users.
After renaming the UI, now it's the time to target new customers & try to build a loyalty with them.