Had caucus chosen someone else – or had someone else even come close – it would have been seen as something of a raspberry at Collins' own leadership and a split in that caucus.
In short, National opted to at least put on a show of being "stable".
There was some surprise when Reti's name was first thrown up for the job. His critics said he was too details-focused, and did not have the political bone in his body.
Those are perhaps the best reasons for him to get the job.
Collins has more than enough political bones to compensate.
He will not overshadow her, and he is also ideal for the times: Reti's medical background and lack of political mumbo-jumbo make him an ideal face for the party during Covid-19.
In short, "Dr Shane" has a good bedside manner for the caucus.
Reti was not the only one talked about before Collins decided on him.
Former leader Simon Bridges did not want it and that was likely a relief for Collins.
There is little more de-stabilising than a deputy who is perceived as wanting the leader's job, especially when the party is struggling in Opposition and leadership speculation is constant.
Dame Jenny Shipley learned that when a young, ambitious English was her deputy back in 2001. By the time English became deputy again to Sir John Key, he no longer wanted the job – until Key told him he did in 2016 when he stepped down.
When Reti suggested English was the model of deputy he wanted to be, the question was asked whether that was the Shipley English, or the Key English. Collins was quick to answer: "I think we are working on the latter."
That does not mean Reti has no ambition to be leader. He certainly did not rule it out, and nor did Collins saying she was sure he would be a good leader one day.
But Reti is not to type to act on such ambition prematurely or recklessly.
There is no one job description for the deputy leader. They can have different roles, depending on the circumstances and the attributes of the leader and the deputy.
Some are relied on for caucus discipline, some are organisers, some simply do the boring bits of the leader's job. In rare circumstances, they are chosen because they are popular – and it is a bid to try to boost the popularity of the leader or the party, as Jacinda Ardern was for Andrew Little.
But the deputy role can take as well as give.
Deputies get little of the glory from success. However, as Gerry Brownlee has shown, they do have to share the failings of the leader and the team purely by dint of being part of the leadership.
Whether Collins' re-shuffle later this week will be as tidy is questionable, but if the caucus needed any reminder of why they had needed to show a solid, uncontested front it came straight after the deputy election.
Several MPs – including Todd Muller - immediately departed on their "roadies of shame", visits Collins has sent them on around the country to listen to the party volunteers give an unstinting appraisal of how badly they had stuffed up over the last year.
As for Bridges, Maureen Pugh was elected junior whip.
Whips decide which MPs get leave from Parliament and who gets "House duty" – the hours in which they have to sit in Parliament's Debating Chamber to make up the numbers.
If Pugh was minded to, she could easily get revenge for Bridges' salty description of her talents last term.
Bridges might want to invest in a comfortable cushion for his chair.
