You can not love a Victoria's Secret model if your earn only 500$/month.Vietnam and Russia have always been pally, why would they buy from Ukraine when they could by from Russia??
Vietnam need cheap weapons (second-hand) of Ukraine (MSTA-B, 2A36, T-72, T-64, BMP-3,AGS-30, Su-24, Su-25, Su-27,Mig-29...). Ukraine feeling boring weapons original from Russia. Ukraine not full financial for weapons standards Russia. They want "delete all" soon. Ukraine think them is waste, but Vietnam think them is "diamond".
In the future, US gorverment support financial and weapon standard NATO, Ukraine cannot continue with weapon's Russia (Not full financial and support from Russia). Ukraine need money, and will sell them with cheap.
Vietnam will repurchase all help Ukraine. Ukraine will give Vietnam technology for development industry defence (vehicle, engine, weapon...).