You’re missing a whole lot of context by cherry picking.
Gruden, his first year in Tampa, won the SB. He then spent 6 more seasons there and never won another playoff game losing twice in the WC round. He took Dungy’s team to the SB.
Bruce Arians did nothing in his first year, got Tom Brady for his next two, and was then promptly fired because he sucked.
Mike Tomlin won the SB in his second season and two years later lost the SB with a Bill Cowher team. Tomlin took over 2 years after the same team had won the SB already. Over the next 14 years the Steelers have won a total of 4 playoff games, losing 6 times in the WC round and missing the playoffs in 6 of those 14 years.
And never mind missing the context that McD had his 7th round rookie QB playing in Buffalo in the postseason and the Dolphins losing by 3 points in that game. And sure, McD lost with Tua in -20F weather in KC (that affected the play of Mahomes, maybe the GOAT, so much that he had his 3rd worst playoff showing ever out of 21 games.) The other two that were worse came very early in his career. And that same KC team went on to beat the Bills, in Buffalo, then the Ravens, in Baltimore, before ending the season with a SB win against the 49ers.