How quickly folks forget all the bullpen moves Farrell made in September once he got some decent arms. Then, presto magico, Kimbrel took a dive, actually several dives, and of course Farrell got the blame.
Let's not forget too that in game 1 of the ALDS Porcello gave up 5 runs in 2 or 3 innings, then Price in game 2 gave up 6 runs in 2 or 3 innings. Porcello and Price took the Sox bullpen (and the manager) out of the equation.
I agree managers can make a difference when they have a really good bullpen as both Francona and Maddon have, but let us not forget the role of the GM's involved. The Yankees Cashman dumped both relievers, Chapman and Miller, the pundits are now raving about. The recipients of this largesse were the Cubs GM Theo and the Guardians GM. They correctly figured out that you can't have too many great arms in the bullpen.
Where the two managers have sort of broken precedent is in bringing those great arms into the games relatively early and relatively often. The simple rule now seems to be: once you get a lead, hang onto it for dear life. This mostly applies, however, to the postseason. During the regular season you need those starterers eating innings.