Well that's a bit of a contradiction if you ask me. A good coach 1 on 1 but not all 11? Out of interest, which players do you think he has developed since being at Everton?
It really isn't though is it? A role of a coach is different to the role of a manager. You can coach a player to be better but that doesn't mean you are well equipped as a tactician does it? Look at Mike Phelan, did most of the day to day coaching at Man Utd under Ferguson but when it came to being a manager didn't quite work for him.
Richarlison is the obvious one, that boy has talent and has improved technically over the time he's been with Silva (but I cant bare Silva's idea of playing Richarlison wide right, tactically its illogical). While not a good premier league striker, DCL has become a better player. Digne has steadied himself, established himself as a top premier league player, we got him for relatively cheap but didn't quite cut it at barca, (al be it due to teh World #1 LB), roma and psg?.
I'm not defending Silva, I think he's remarkably lucky to be in the job after his 3 wins in 16 games spell last year, but im pointing out that the players by all reputable accounts like him and he appears to be a good coach, just not a good Manager. Also should be noted players improvements can be down to the other coaches as well.