I think that Higuain before this season scored something like 2 goals in 20 CL knockout games. It was a pretty atrocious record for a player of his profile.
Many of them thought that Morata could develop into great striker or good enough to still win them Seria A which is something they are used too and seen him as someone who thrives in CL, a competition they want so bad. In other words, they've seen Morata as a big game player with much space to improve and many of them were willing to gamble on that. Of course, you could find other opinions which were more for the safer option (Higuain) but a number of people wanting him to stay, even pay more money to Real, was speaking for his qualities by itself.
Understand where you coming from and what concern you have. I'm also not sure, but the thing is you never can be. Btw. when you look Morata you are talking more about peak Torres level from Liverpool. And when we are at it, Torres with all his minutes in Atletico managed to outscore Morata's last season only once and that is by a single goal. He came in Liverpool 1 year younger but he was perfectly suited for Rafa style of play. I hope we can get the same from Morata.