You forgot "target emerging markets", which is an important reason that Xiaomi and Huawei have been successful. Nexus phones also weren't really successful and

You forgot "target emerging markets", which is an important reason that Xiaomi and Huawei have been successful. Nexus phones also weren't really successful and weren't intended to be. They were intended to be development devices and for Google to show the direction that they wanted Android to go in. They also didn't build any of them in-house, they were made by HTC, Samsung, LG, Motorola, Huawei, and Asus. Google's real entry into the smartphone market was with the Pixel which was a direct competitor to the iPhone.