In that game, not only Giannis is having a hard time but the other core players as well. We also have to take note that the majority of Bucks field goals attempt were not contested meaning they are literally having a bad night. A total lockdown to Giannis might be effective but not always the key to slow down the Bucks.
But kudos to Miami Heat for giving Bucks a hard time on that game. That bad night's performance by the Bucks is because of Heat's impressive performance on that game. They destroyed the rhythm of the Bucks offense. They are now 2-0 against the Bucks this season which is a good thing to see as we want to see a close competition in the Eastern Conference playoffs and not just the usual favorites Bucks, Celtics or Raptors.