For the second time in the series, India triumphed inside three days to dash Australia's hopes of reclaiming the Border-Gavaskar Trophy.
The touring side appeared to have the upper hand in the match when they resumed on 62-1 on Sunday looking determined to bounce back from their innings defeat in the series opener in Nagpur.
But with spinners Ravindra Jadeja and Ravichandran Ashwin bowling unchanged, Australia collapsed to be all out for 113 half an hour before the lunch break.
Several batsmen played reckless sweep shots only to fall lbw or be bowled by the Indian spinners.
"I thought they bowled really well, it's not easy out there, but perhaps some guys went away from their methods," Cummins told reporters after his team's six-wicket loss.
"Each batter has their own way to go about it. I don't think there's any one-size-fits-all rule.
"Unfortunately, quite a few of us got out with kind of cross-batted shots which might not be our preferred method."
Australia began their second innings well on Saturday, especially Travis Head, who top-scored with 43 at a run-a-ball.
"Two big things we talk about is the tempo of the game and the method. Maybe at times a little bit too high tempo," Cummins said.
India captain Rohit Sharma explained why the home batters seldom played the sweep shot in Delhi.
"We played on red soil in Nagpur and here you have black soil," said Rohit.
"Sweep is not a safe option here. My personal view is stepping out and playing straight is a better option on this type of soil. Of course, different batters think differently.
"Overall, batters need to have confidence in their method of scoring runs. You need a clear plan how to bat on a particular type of wicket.
"Runs are especially crucial on wickets like this. You have to play your shots to score those runs and these things we discussed on our batting group meetings."
