Tony Abbott stands down as the prime minister last Tuesday. Picture: Ron Foley

Howard Government-era ministers Peter Costello and Amanda Vanstone were among the party stalwarts to speak in favour of the change of leadership on Monday night’s Four Corners, which examined Mr Abbott’s downfall.

Mr Costello, considered one of Australia’s most effective treasurers, told the ABC program that “it looks like it was the right decision”.

His reasons were chillingly pragmatic.

“Here’s the rule in the Liberal Party: If you win you did the right thing,” he said of last Monday night’s leadership coup.

“The Liberal Party really only rewards you for an outcome. If Malcolm had challenged and lost, he would have done the wrong thing, but he challenged and won so the Liberal Party regards it as the right thing.

“The Liberal Party doesn’t give you any great rewards for loyalty — that’s not what it rewards. The Liberal Party rewards success.”

Liberal senator and Abbott supporter Cory Bernardi slammed the plotting as “treachery of the highest order”, but Mr Costello rejected this assessment.

“This is the thing about politics. You’re elected in, you’re elected out. No point complaining about a ballot if you’re in the business of politics. That is the business of politics,” Mr Costello said.

“You want to be a surgeon? Don’t complain about blood. You want to be in politics? Don’t complain about a ballot. That’s the way you get in; that’s the way they take you out.”

THE CREDLIN FACTOR

‘De facto chief’ … Tony Abbott’s chief of staff Peta Credlin in the House of Representatives. Picture: AAP Image/Sam MooySource:AAP

Much of the hourlong program focused on the key role Mr Abbott’s chief of staff, Peta Credlin, played in his demise.

Former Liberal Party treasurer Michael Yabsley told the program that she had become the “de facto chief” who had done damage to a “raft of relationships” that Mr Abbott needed.

“In so many respects, she came to have the role with the prime minister’s colleagues that the prime minister should have had and this made her an extraordinarily powerful person,” he said.

Ms Vanstone, a former Liberal senator, said, “People felt she was more of a doorway blocking off access to the prime minister rather than a bridge”.

THE SLOW DEMISE

Former prime minister Tony Abbott at his home in Forestville, Sydney, after being kicked out of office. Picture: Brett CostelloSource:News Corp Australia

Both Mr Costello and Ms Vanstone pointed out that Mr Abbott was a remarkably effective opposition leader, but those skills didn’t translate into his prime ministership.

“You do need to remember that you can’t build yourself up by pulling other people down,” Ms Vanstone said.

Four Corners proceeded to track Mr Abbott’s slow demise, beginning with his deeply unpopular first Budget.

Mr Costello said Mr Abbott failed to adequately explain the problems the Budget aimed to fix, and that many of the measures — such as the GP co-payment — were “unwise”.

“It just wasn’t worth using political capital on them,” he said.

“The public felt they were getting a really tough treatment for some kind of sickness that they really didn’t understand.”

Tensions came to head when Mr Abbott decided in January to appoint Prince Philip as a knight.

Mr Costello openly mocked the knighthood fiasco, when recalling that he was at a barbecue on Australia Day when the news reached him.

“You talk about a figurative barbecue stopper. This was a literal barbecue stopper,” Mr Costello laughed. “Didn’t expect that one on Australia Day.”

Ms Vanstone said the knighthood debacle showed Mr Abbott was “extraordinarily out of touch”.

Mr Yabsley said it was “an awful call” that had the “makings of an April Fool’s Day prank about it”.

Four Corners then ran the gamut of gaffes that plagued Tony Abbott this year, including onion eating, his “holocaust of job” losses comment, and his threat to “shirt-front” Russian President Vladimir Putin.

After a failed leadership spill in February, Mr Turnbull finally achieved his long-held ambition last Monday, winning the prime ministership 54-44.

Four Corners gave the last word to Nationals deputy leader Barnaby Joyce, who said the next knifing would likely come from the other side of politics.

“Turnbull is going to beat [Bill] Shorten — and everybody in the Labor Party knows that,” he said.

Four Corners will be replayed on ABC on Tuesday at 10am and Wednesday at midnight. It can also be seen on ABC News 24 on Saturday at 8pm, on ABC iview and at abc.net.au/4corners.