From everything I've seen, the Royals where planning on taking one top pitchers, but none fell to them. At that point I think taking Starling was probably the best choice at that point. There was a ton of risk involved with most of the players left (there always is in about 99.9% of baseball draftees) while Bubba probably represented the highest ceiling of anyone left, possibly of any player in this years draft. I've seen him described to as close as major league ready defensively as someone can be who has not focused exclusively on baseball so at the very least the Royals will be getting a quality defensive player at a premium defensive postition and the speed to steal bases. The biggest concern with him is that he hasn't faced high quality pitching, but he's pretty much destroyed the pitching he has faced and any 18 year old is going to need some work batting wise.
As far as signing him goes, they Royals have actually had a decent relationship with Boras over the last few years. Not great (no one has a great relationship with Boras, just whoever throws out the most money) but good enough that he's at least let the Royals in the door as far a negotiating goes. If he doesn't sign the Royals would get a equal pick next year so all the people saying that Starling isn't any good could then complain the Royals didn't sign him and the Royals could grab someone else next year.