The french corporations are not interested in selling trains, they're interested in making Profit ON selling trains, and the lack of profitability is blatantly clear in light of the low amounts they've invested in the form of loans

Selling trains to a public service state entity in Vietnam is not profitable in itself, the loan is a ticket purchase for access to Vietnamese resources or industries that are profitable when invested in

What the French are purchasing access to isn't specified publicly, but it sure as shit ain't access to build rail for working class Vietnamese in the form of sub-strandard inter-industry foreign loans