I think it has a lot to do with its government having laid out a plan since the 90s to develop its IT industry.
Results are:
1) Lots of IT grads 2) Lots of funding 3) Okay-ish infrastructure
If we add this to the interests in entrepreneurship among Vietnamese people, it results in a strong tech scene.
He traveled to Vietnam and observed a high quality Computer Science education in primary / secondary school. Talking about grade 11 scholars, he wrote:
After returning to the US, I asked a senior engineer how he'd rank this question on a Google interview. Without knowing the source of the question, he judged that this would be in the top third. The class had 45 minutes to design a solution and implement it in Pascal. Most of them finished, a few just needed another five minutes. There is no question that half of the students in that grade 11 class could pass the Google interview process.
I have seen university students in my German CS classes struggle to implement breadth-first search; I would by highly surprised if an average grade 11 student could write a program to compute the connected components of a maze in less than 45 minutes.
I know Malaysian companies that have back-offices in Vietnam because of the great talent there. The lack of English is a hurdle, but not impossible.
While I realize this isn't exactly related to start ups it is interesting because in order to produce and support esports teams, and especially true if the team is any good, a couple of things must be true.
1) Large population of adolescents/young adults with regular access to internet.
2) Large player base to produce quality players.
3) Money from sponsors who see it as a viable marketing venture.
The fact that Vietnam has been able to do this bodes well for them.