Club record signing Mounie was twice left unmarked in the first half and took advantage to bundle Huddersfield into an early lead and then head home his second as Wagner’s side ended a four-game losing run in the Premier League.
Mounie, signed for a reported £11.44million plus add-ons from Montpellier in the summer, marked his Premier League debut with a double at Crystal Palace on the opening day, but had not scored since and has recently struggled with a heel injury.
“He had a difficult period with his injury, but to be honest we all had the feeling he would be able to perform like he did today because in the last two weeks he has looked very good in training,” Wagner said.
“We’re very happy that we have him back at his best and with Laurent Depoitre, another very good striker, because we’re totally aware about the busy period that is in front of us.
“Both of them are healthy and fit and Steve for sure was a threat today. All the other offensive players as well were very dangerous today. We were able to create a lot of good opportunities.
“Offensively for sure this was one of our strongest performances of the season.”
Huddersfield leapfrogged Brighton into 11th place in the table, while the south-coast club slipped to 13th as their winless league run was extended to five matches.
“It was a very good performance from the defence to the offence, from the stands to the grass, there was energy, aggression, desire, everything what we wanted to show,” Wagner added.
“We know if we are to get wins in the Premier League, we have to over-perform and the players have done this today on the highest level.”
Brighton boss Chris Hughton agreed his side had been second best in front of watching England boss Gareth Southgate.
“I’m incredibly disappointed,” Hughton said. “Huddersfield are a very good side at home and if you afford them the goals that we did it becomes very difficult.
“We never allowed ourselves to get into the rhythm we needed to. Certainly the better team won today, but the two goals, particularly the first one, were most disappointing.”
Hughton said centre-half Lewis Dunk, one player Southgate will have been keen to observe, let his performance levels drop.
The Brighton boss also explained why he chose to leave Anthony Knockaert out of his matchday squad.
“I just made a decision,” he said. “Their full-backs play very high and wide and I felt we needed to be compact.
“The team formation didn’t have anything to do with the goals we conceded.”