Imagine if Motorola, Cisco, and Qualcomm merged to form one entity. That's similar to Huawei. They have excellent brand awareness and product recognition as a result of their history, diverse areas of R&D, and global business. In terms of technology, Huawei builds their own processor, baseband, WiFi, and power management chips. Only Apple and Huawei are shipping 7nm products. Huawei has about 10 retail stores per city with excellent offline presence.
Imagine if Logitech developed smartphones, personal electronics, and sold only online. That's Xiaomi. It's a brand recognized by younger customers but not mainstream customers. Xiaomi was a hot brand 5 years ago, but Huawei's resources and focus on smartphone R&D made them leap ahead. Xiaomi sold only online so that limited them to certain groups with a high geek factor.
Oppo and Vivo both focused their efforts on offline sales in middle-class cities in China. Hundreds of millions of middle class consumers bought Oppo and Vivo. That generated revenue to invest in R&D. Consequently, Oppo and Vivo were able to leap ahead of Xiaomi and showcase premium phones like Find X and Apex.
The typical rich millennial wants a Huawei phone, period. It's a premium phone with 3 Leica lenses, a large phablet display, and has the latest technologies like Face ID. The hardware features and specs are objectively better than iPhone. Apple is seen as a "not invented here" brand that offers no real advantages. And to boot, there's a trade war going on.