I think in addition to i think him was also been friendly and familiar with the teams just as you have made mentioned the coach had long time know the player staffers, and other teams, pulse i think the coach has established relationships with the player.
What really killed the Super Eagles recent matches were the coach fault because he selected those players so we should not blame others and the next persons to blame are the players. They would have using this opportunity to do well so they can be used in other games and like this I don't think those players can be used in any other international games but in local games.
The coach was not having much experience on the players and that is why the technical crew is with him to direct and select the players because they know who is who.
You are kinda of right the coach decisions can really have a significant impact on the team performance, which it's also important to consider the players perspective and the technical crew's expertise in the players selection, this is why may have views on international matches as opportunities to showcase their skills and learn physically and also showcase their skills and potentially earn more playing time.
Everything works interwoven for the benefits of the team to grow and achieve altogether, because if the coach make the selections of players to use and they all failed to deliver by working not been coordinated, in football, the decision and pattern right from the top down to the players must be in the suitability of the progress of them all, because if they win a match, the entire team will feel the pride and it can also creates more opportunities for them to arrive early on other achievements in their career, so I don't blame anyone on this regard, except that they all have to work in line.