I think many different factors came in to Everton being let down a bit. First of all the market for players was just out of control. The kind of money being thrown around for bang average players (because of the new TV deal I suppose) was ridiculous. I think we all (even the club) got a little over hyped with our new supposed war chest and just figured we could buy whoever we needed and that those players would come to us. Our ambition was there, but the deals just didn't get done for one reason or another.
After consecutive 11th place finishes, RM left us in a place where we don't seem to be an attractive club to 'premium' footballers yet. We tried to poach players from some big clubs but they ultimately choose different options for their careers. The transfers we did get in are great in my opinion, but just look at the clubs we got them from. Palace, Villa, West Ham, Fulham, Swansea. All of those players we got saw Everton as a step up in their career and rightfully so, but it goes to show that its hard to attract a bigger name to a rebuilding process of sorts.
I think even though our manager was let down a little bit, he still has the ability and our squad has the talent to do big things this season. Once we are contending for a European place again, more players will want to come to us. We have a vision, but sometimes its hard for people outside of the club to be convinced of that until they see results. The Moshiri/Koeman era is just in its infancy. There are going to be some bumps on the road ahead, but our future is brighter than ever.