VIDEO: Cheika not blaming red card for thrashing
Cheika, who was subjected to a World Rugby investigation because of his reaction to officiating decisions in Australia's 6-30 defeat against England, had no argument with French referee Pascal Guazare's decision to send off Kepu for smashing a forearm into the head of Scotland flank Hamish Watson – at a time when his team were leading 12-10.
"I've watched the footage just now and the referee really didn't have much alternative, I don't think," conceded Cheika, who felt there was no intent in the actions of his front rower.
"Just from the point of view of Kepu, he's got no intent to take the player in the head," he added.
"The player [Watson], when you watch him, his back leg slips underneath him, so he goes lower than Kepu's aiming."
Australia, who were beaten 19-24 by Gregor Townsend's improving Scotland side in Sydney in June, had not previously conceded more than 32 points in a game against the Scots or more than three tries, but ended up shipping 53 points and eight tries.
"I don't see the red card as an excuse for losing that game at all," said Cheika, whose team beat world champions New Zealand 23-18 in Brisbane last month.
"It was unfortunate but it definitely wasn't the red card. That happens in matches.
"I don't think it was a turning point. I thought we could have still won with 14 players.
"I think the big thing for us will be to try and improve our mindset – get away from maybe not fully believing in ourselves, that we can go out and do the job no matter what the conditions.
"I don't think that we've gone on and said, 'We're going to do this with 14 players,' or last week, 'We're going to do this against the odds, when we were down.' We just need to take that little bit of extra step in maturity."
In hooker Stephen Moore's farewell match, after 129 caps, Australia also had fullback Kurtley Beale yellow carded in the 78th minute and bagged four tries of their own, courtesy of centre Tevita Kuridrani (two), Beale and replacement lock Lopeti Timani.
Scotland lost their star player, fullback Stuart Hogg, to a hip injury in the warm-up, switching wing Sean Maitland to the No.15 slot and giving a first start to South African-born Sale wing Byron McGuigan, who scored two tries.
The other home tries came from Ali Price, Maitland, Jonny Gray, Huw Jones, skipper John Barclay and Stuart McInally.
"It was a big advantage to us when your opponents have to play 40 minutes with one man down," admitted Scotland head coach Townsend, who was delighted that his players maintained their focus after the late loss of Hogg, and backed up their impressive showing in their 17-22 defeat by New Zealand last week.
"There's been a lot of positivity around Scottish rugby. A lot of hard work's gone in at a number of levels over the last few years and it's great to get that win against the current number three team in the world."
Looking ahead to the new year and the 2018 Six Nations Championship, Townsend said: "We've just got to build on this and make sure this energy, enjoyment and hard work keeps on going because we've got some big tests coming up – Wales, France, and England.
"Our next three games are really going to test us. Those three are excellent teams but we've got to go into the Six Nations with real confidence that we can do well."