I only watched the highlights. From the highlights, it looks like Dimitrov hit everything super early by hugging the baseline. Rallies were generally very short, Dimi took time away from Alcaraz. Didn't let Alcaraz push him back with the topspin, as a matter of fact, Alcaraz was forced to play Dimi's game. Quite a few points where Alcaraz didn't expect the ball to come back so early or didn't expect Dimi to hit winners.
Dimi's FH seems to be also more efficient & compact. The speed difference between Dimi's FH to that of Alcaraz was quite obvious. This may not be a factor in clay, but on hard court it's a different story.