For many it is a big deal to have someone in a position of leadership who has been in their shoes and knows their culture and can relate to them in a way others cannot. I think that's one reason BYU has always tried to have at least one African American coach on their staff (now they have 2).
With Kalani, I don't think BYU was naive to think that simply hiring a Poly as HC would open the floodgates to all top Poly recruits to come to Provo. I mean we've had Polynesian coaches on the staff before. But I do think there was a feeling they were losing ground with their Polynesian pipeline and Kalani was the guy to try to correct that situation.