Russia is insignificant, and I believe the Vietnamese are growing up /maturing to see that a total dependence on Russia is antagonistic for Vietnamese aspirations for regional plans as the premier power in continental south east asia. Vietnam understands that the United States' pivot is for long term and the consequence for this is America's increased interaction with regional players. There are rewards and blessings to cooperation with the United States, this includes military sales and investment(s). The Vietnamese see this. They are not stupid.
There is a saying, my friend. A man who eats only gruel doesn't know how prime rib tastes like. But once he tastes prime rib or skirt steak, he'll never go back to gruel again.
Here's to increased bilateral ties.