Papua New Guinea's new government says the ousted administration was dragging its feet over the issue of Sir Michael Somare's health and that this presented the opportunity for a change of leadership.
On Tuesday, fifty members of the then government defected to the opposition to have the Prime Minister's office declared vacant because of Sir Michael's prolonged absense due to ill-health.
The parliament then voted to replace acting Prime Minister Sam Abal with Peter O'Neill.
The ousted government had been pursuing a constitutional process to independently verify whether Sir Michael was unfit to continue.
But a senior MP with the then opposition, Bart Philemon, says enough time had been wasted already.
"We felt that it was going to be another twenty-eight days. Sir Michael's family had already declared his unsuitability to continue even if he was discharged from the hospital. And from what we know, I think they'd used this deliberately as a cover to see how long they can stay in power."
Sam Abal has vowed to fight the vote against him in court, saying the ousting was unconstitutional.
He appears to have good legal grounds according to a constitutional lawyer, Peter Donigi, who says the position of prime minister wasn't vacant in the first place.
Yet Mr Donigi says if Sam Abal is re-appointed, it could spark a constitutional crisis given the oppostion, led by Belden Namah, won by 70 votes to Mr Abal's 24.
So that's a substantial majority there, and if Mr Abal is successful in his court [case] and is re-instated, the question is how can he manage the purse of the nation, in view of the fact that he does not muster the numbers, and the opposition, led by Mr Namah, would make it very difficult for him to perform. And therefore we will have a constitutional crisis.
Dr Ray Anere from the National Research Institute says general dissatisfaction with the Somare regime, which had become embroiled in accusations of financial impropriety against leading members, ultimately led to the defections.
They felt that the country needed a firm and strong and decisive leadership which was not quite there when Sir Michael had left the country (to go to Singapore for medical treatment); and also the state of disarray on the part of the National Alliance party of which Sir Michael is the strong man. So all of those put together, they felt that there had to be a change in leadership.
Dr Anere says Peter O'Neil's emerging cabinet line-up - which features several former top ministers from the Somare administration and two former Prime Ministers - holds vast experience.
If we look to any indications of confidence here, it'd be the private sector and the business houses. The business community here in PNG has expressed their confidence in the new government given the line-up of ministers. And so we look to the private sector - if the private sector is confident, then I think the people of PNG can at least have some hope in the new government.
Peter O'Neill is expected to unveil the full list of cabinet portfolios by the weekend