Symbian sucked. It required rewriting all your code to use a cleanup stack which basically was one of the crappiest C hacks in history. And every Symbian phone had a different UI toolkit that required at least recompiling, sometimes new ports. And Symbian devices never had enough CPU or RAM because some idiot thought that users would rather have a shit phone that didn't need to be charged daily. Never use Symbian as an example of anything other than the wrong way to do it.
Windows Mobile was a PDA OS that just never evolved into a phone OS, it required a pen or sharp fingernails. It was however the best mobile development experience for over a decade.
Windows Phone failed because Ballmer was a total moron. The moment he and Elop came out on stage wearing suits with sweat stained arm pit and geeked out on how cool Windows phone is, they guaranteed that no one with a sense of fashion would go near it. But what really killed it was that C# was the only way to program for the phone. Sure, Unity is C# friendly, but every app would have to be entirely rewritten for Windows phone. This would have potentially made Windows phone the most secure ever, but no one is ever going to invest in fully rewriting everything for a single platform. So the app store was nothing but porn and gambling.
Palm was a PDA OS, it was never anything else. Actually, PalmOS never even evolved to PDA, it was a PIM OS.
BlackBerry failed for many reasons. Mostly, they ignored the world market. They just didn't exist anywhere outside of the US and Canada. China, Russia, Africa, South America, the middle east and more are a huge market which Huawei will succeed in. BlackBerry was only available to a very small number of people. I never saw a Blackberry outside of the lab or on TV. Another major fail was selling it as a secure device. It wasn't.
Apple succeeded almost entirely because they're a fashion brand that makes tech. Oh, and releasing the first generally available multitouch phone with a fast CPU, lots of RAM and a web browser that was actually useable helped. And... it worked with iTunes. Nokia, the closest competitor at the time had the crappiest music experience imaginable. They couldn't even make a decent music store in Finland.
Android worked because it was the only commercially supported OS basically free for use on any phone (initially) so vendors LOVED. Google made their money from the customer. Of course, it's a crap deal for the phone maker since Google gets all the reoccurring income... Which is HUGE. But Google and Microsoft were the only companies that could ever have competed against Apple and Ballmer screwed that up on an unimaginable scale.
Huawei will compete in some markets without a problem. They will need to hire massive numbers of developers in Kenya to truly compete. This is due to English fluency. The HarmonyOS is currently poorly documented in English. Kenya is the only non-NATO country with decent English skills. So, making Kenya a major development hub for Harmony would be brilliant.