Both players were fined $15,000 by the NBA on Sunday.
Officials on Saturday hit both players with double fouls as well as double technical fouls, which resulted in them being tossed.
The players boxed each other out aggressively under the rim, then had to be separated after exchanging pushes, with referee Kevin Scott in the middle.
Ennis then threw a closed-fist forearm shiver to get Bucks assistant coach Darvin Ham off him as members of the coaching staff tried to intervene during the scuffle.
Williams said Sunday that he was surprised at being ejected.
"I've played in a lot of basketball games in the NBA, seen a lot of different things, been involved with things obviously throughout the course of my career, but I don't think either of us should've been ejected," he said. "I've seen a lot more take place from guys that received a lot less punishment. I don't think he should've been ejected, I certainly don't think I should've been ejected so yeah, I was very surprised, especially with no explanation.
"We weren't even told why we were kicked out. There was no swinging, no punches through, no open hand swings. It was literally just shoving. For guys to get kicked out for shoving, I've never seen that before personally."
It was the fifth ejection of Williams' career (second playoff ejection). Ennis had never been ejected before Saturday.
"Marvin's toughness, Marvin's competitiveness, our group, our edge, that's important to us," Bucks coach Mike Budenholzer said. "We certainly don't want to ever not have that edge and not have that physicality, have the competitiveness, and hopefully you can stay in the game and things like that don't happen. But Marvin is a pro, and we're just fortunate to have him and his toughness."
Milwaukee went up 2-1 in the series with a 121-107 victory. Reigning MVP Giannis Antetokounmpo finished with 35 points, 11 rebounds and 7 assists, and he was 12-for-14 from the field. He is the first player in NBA history with at least 35 points, 10 rebounds and 85% shooting on field goal attempts in a playoff game, per ESPN Stats & Information research.
Antetokounmpo scored 21 points while making all of his shots in the first half. He said he didn't see the pushing match between Williams and Ennis because he was on the bench. It did serve as a spark for the team, though.
"At the end of the day, a guy sacrifices himself for the team and as I said previously, we've got to pick it up for him," Antetokounmpo said. "What he did, he's got to miss time for the team, so we were even more locked in and played harder because that's what a good team does."