A few of those players actually worked out, with Herrera's decline being unexpected (even before the final development). Where Klentak really botched things, in a way that wasn't entirely his fault, was casting his lot with so much of what he inherited (including the manager - like the Astros and Cubs weren't not going to win until our third manager, but we waited longer to get one). Hernandez, Franco, Altherr, Williams, Pivetta, Eflin: all still pieces in 2018 and still on the roster in 2019, all but one gone now. And no young players to replace them.
It certainly didn't help that Klentak's first draft and biggest rebuild trade (Giles) ultimately produced so little.