It comes after Crowe famously blew up at Keary at a Rabbitohs pre-season bonding session, telling his star player, "You didn't earn your money last season".
It resulted in Keary walking out of the bonding session at Crowe's Nana Glen farm before the 2016 season.
From that moment on Keary was reportedly on the outer at the Rabbitohs before he was signed by Roosters coach Trent Robinson, who was searching for a halves partner alongside Mitchell Pearce.
Keary's response to his Rabbitohs humiliation has been emphatic.
As of Friday afternoon, Keary leads the competition in try assists for the 2017 season and has been instrumental in the Roosters' wins over the Titans and Bulldogs.
"We know that he was going to be one of the buys of the year," Johns told Triple M's Grill Team.
"A sensational, tough young player. Souths must be watching him playing going, 'Oh my god. How did we let him go'.
"He really should have been a Rabbitoh for life. They've absolutely stuffed up on that one. When you've got a player like that you keep him."
When Keary was putting the nails in the Bulldogs' coffin on Thursday night at Allianz Stadium, NRL fans were poking fun at Crowe and his rugby league intelligence.
Keary was in January overtly diplomatic in his response to his falling out with the Rabbits.
"I guess you'd say we're on good terms, I don't know," Keary told Fox Sports.
"Once you leave a club you don't really keep in contact too much. I guess you'd say good terms.
"Definitely good terms with all the boys there. We had some really good times over the four or five years I was there.
"I wouldn't have done anything different on my end, it's footy isn't it? No one really gets to stay at one club any more do they? That's just how it is."
"You learn from things like that and it's not ideal, but it's something that happened."
He appears to be letting his football do the talking.
The Rabbitohs host the Roosters in a round four blockbuster on Thursday March 23 at ANZ Stadium.
