Style of leadership, it isnt that "hes not a good IGL" its more of a "its not his comfort style"
For international rosters the difficulty comes from properly understanding and relating to your fellow teammate, since none of you share a basic background that takes time.
FNS's style of IGLing is as we know is very cerebral and tactical, that means he needs the utmost cohesion with his team, cohesion which would not be present if needed to be created. International Rosters outside of EMEA are not made from "friendship" or networking between players, but from cold and calculating management, they aim for the best result by getting the best players, the problem is that Team Synergy and Relationship end up the responsability of the IGL, and that is simply not FNS style, he picks players from which he knows and trusts, or sees potential, the base of relation is already existent.
Someone like Sadhaak or Boostio could work. But IGLs like Stax and FNS wouldnt work