Why did Capablanca win a majority of games playing as black? The first-move advantage is said to make it slightly more likely for white to win. This is shown in many databases of chess games, such as chessgames.com which shows the following results:

White wins 294,068 games (37.57%)
Black wins 216,938 games (27.72%)
271,659 games are drawn (34.71%)

Despite this, Capablanca actually had a higher win rate when playing black compared to playing white. Of course there is always an exception to the rule, but what aspect of his play makes him different to all the other players of his time?
In Megabase 2016, Capablanca played 791 games as White and won 52.6% of them, and played 406 games as Black and won 48.5% of them, so he didn't win more as Black but it was surprisingly close.

The discrepancy between number of White games and Black games was surprising, so I broke out his simultaneous displays (in which he would generally be playing White). In his simuls, he played 304 games as White and won only 40.8% of them, and played 26 games as Black and won 34.6% of them.

When we subtract out the simul games, he won 292/487 = 60.0% of his games as White, and 188/380 = 49.4% of his games as Black.

In conclusion, I suspect that the unique aspect of his play was that he didn't try that hard in simuls.