The primary difference between beating a team in the regular season and beating them in a playoff series is repetition. During the regular season you e scouted, but only have a day or two prep. In a series you’ve got a week or more to learn and adapt. Players already have familiarity with one and others games having played each other for years. So it comes down to . . . coaching, strategy and adjustments.
Though players have good games and bad, and some fold, on average they typically don’t get better or worse during a series. But good coaches learn their opponent’s tells and idiosyncracies and figure out ways to attack and defend them and make adjustments. Worse coaches (and mind I’m saying “worse” not bad, it’s comparative) fail to make adjustments and it’s why you see those teams tend to struggle the further into a series it gets unless their players rise above the coaching and carry their coaches.
Very simply, monty never gave us an advantage at the coaching level in playoff series.