What factors defines being successful in the Vpop/vietnamese music scene?  

Money talks so I think all the above. You know when an artist is big when they get the big names behind them like Samsung, Grab, Lazada, Vinfast or Oppo. The less popular artists get deals with small businesses like their local coffee shop.

In recent years, V-pop has started to receive a lot of attention from the international community because of young singers with completely new music styles such as Son Tung M-TP, Vu Cat Tuong, Min, Amee, Hoang Thuy Linh, group Monstar... Many songs and albums have entered many prestigious international music charts.
and I think that is also the reason for singers to invest more MV, better sound quality before the product launch.