Now was Benintendi ready? Who knows - they have given him a lot of responsibility very quickly and he has adjusted. I think this was always possible - the org made their denials, but that's what you do. Maybe they were hard on Beltran and missed out - but he can barely move anymore.
I think to address earlier points - while it is fair to wonder whether the treatment of Bradley held him back, I'd counter that Bradley had conclusively proven he can hit minor league pitching. A demotion for him - given what he had to work on - was not going to accomplish anything, aside from giving him a potential sense of senioritis. His adjustments had to take place at the big league level.
Benintendi is a different kettle of fish - and as Dojji notes, he will struggle eventually - because he plays baseball for a living, and all baseball players go through those patches. The org bet is that he has the makeup and physical talent to figure that stuff out when it comes up. Everything about his brief minor league career backs that sentiment. What a week with him with the big league club shows to me - fairly conclusively - that he at least physically and skill-wise belongs in the show ... he does not look overmatched. (well, aside from his 2nd career AB in the bottom 9 against a fireballer closer sort)