Many invest in a country usually not because of the people who excel in mathematics. but they choose where it is strategic and the production costs are low. for mathematical intelligence it is related to how the individual's career will be, not with the country
I agreed with what you said because companies or groups that invest in country that have huge number of students winning the Olympic award in mathematics while the country itself dont have the required resources, commended tax per production and infrastructure the investors or company will bankrupt, so OP the companies that moved to the Southeast Asian countries dont actually moved of they have numerous students that won high prizes in Olympic math.