Through most of the season, Holiday did not play any better than Brogdon did last season. But he came on in the playoffs and probably most importantly, stayed healthy. Brogdon only played 39 games but was good, not as good as Holiday, but good (41.2% from 3 for example). Robert Williams played 6 games.
Durability or availability is very important. That is what made the difference. It took a lot to get Holiday, but now that we have won a title, with Holiday playing a key role, hard to see much left to debate around this trade.