https://en.wikipedia.org/wiki/Sino-Vietnamese_conflicts,_197...
Also let's not forget how pushy china has been in West Philippine Sea ("South China sea") east of Vietnam.
https://en.wikipedia.org/wiki/Chinese_domination_of_Vietnam
The Chinese domination of Vietnam began in 111 BC, and is usually considered to have ended in 938 AD. A fourth, relatively brief, 20-year punitive invasion by the Ming dynasty, 400 years later, is usually excluded by historians in discussion of the main, almost continuous, period of Chinese colonization from 111 BC to 938 AD, as is the brief occupation of northern Vietnam by Chinese forces at the end of the Second World War.
Not I supporting Huawei (I think they better off died), but I don't think that War argument is the full picture.
As far as I know, Vietnam's Internet giants is far smaller compare those in China and U.S. So even if Vietnam going to full-boom in 5G (That currently require equipments from Huawei to keep up to the speed), that will still be more beneficial to international companies than domestic ones.
Maybe that's another reason why they're willing to claim down and making decision with such leverage.