That’s not true...Huawei stole from Nortel and it’s just that tech initially. Samsung was doing great before the forced anti Samsung protests (Huawei was already 1 at the time).

i'm a former nortel employee. so sad to see people lose their houses and pensions due to chinese theft. The hacking wasn't even publicized as a warning that other companies could heed - get your security in order, be careful with your IP, or you will go from 140,000 employees to a small cadre of lawyers and accountants managing the pittance that is left over. But at least none of the management at Nortel was embarrassed by the bad publicity of getting owned by the chinese and their inability to do anything about it.

Isn't the cause of Samsung's decline in China due to boycotts related to THAAD deployment in SK?

Yes. THAAD was the reason.

Samsung is making a killing on selling OLED screens to both Huawei and Apple - I guess they figured it's easier and more profitable this way than to try re-conquer a saturated market.