How soon, though, was anyone's guess.
"We didn't think it would be two years, that's for sure," Leppitsch told AAP.
"Neither of us thought we could turn it around that quickly, so it's awesome.
"We've got a great group of people and great staff, so who knows, maybe (we can win) a few more."
Leppitsch and fellow former senior coach Brendon Bolton were among the first people McRae brought into the fold when he took over at Collingwood in September 2021.
The Magpies had parted ways with favourite son Nathan Buckley, finished 17th and looked miles off contending.
McRae and co engineered a stunning rise up the ladder, firing the Magpies into a preliminary final in their first season before taking the big step to a premiership this year.
It was sealed with a thrilling four-point win in Saturday's grand final against the Brisbane Lions - the club with which McRae and Leppitsch won a famous hat-trick of flags as players.
"It's really driven by Craig and what he implemented, the family approach and the game style," Leppitsch said.
"Then the players have to buy in because if they don't buy in you don't get the result.
"It takes everyone to be pushing in the same direction and we've got that."
Leppitsch didn't reach finals during his three years as Brisbane's senior coach - from 2014 to 2016 - but adds the Magpies' latest success to the three flags he helped engineer as an assistant to Damien Hardwick at Richmond.
The 48-year-old described the experience of winning a premiership in an off-field capacity as being "completely different" to that which players feel.
"Coaches and support staff are here to help the players do that, so you're just rapt for them," Leppitsch said.
"To give them that experience that I was lucky enough to feel as a player is awesome.
"It's a bit like watching your kids win a premiership ... the feeling is the pride of watching your sons go out there and do it.
"They're premiership players now and nobody can ever take that away from them."
Leppitsch still has close friends at Brisbane and said he felt for them as he celebrated Collingwood's grand final triumph.
"It's heartbreaking for them and it would've been heartbreaking for us to lose as well," he said.
"Any time that you've got a grand final decided by under a goal, someone's going to walk away flat and disappointed."
Leppitsch had a 21 per cent winning ratio as Brisbane coach before finding instant success on arrival at Richmond in 2017.
He said a return to the hot seat isn't on the radar.
"I'm not even thinking about it, to be perfectly honest," Leppitsch said.
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