Speaking to Australian broadcaster Mark Howard, McCullum opened up on what a joke the captaincy selection process was.
"They asked Ross and I to push our cases in a presidential style election to present Powerpoint presentations for the captaincy. It was ridiculous to be honest," McCullum told Howard.
"It was in a meeting room with Powerpoint presentations and all that. It was just a crock of s***. it was terrible.
"If I made a mistake anywhere along the road it was actually doing that, it's ridiculous.
"If someone wants you as captain then they want you as captain, if they don't well so be it, it's not your right that you should be captain ... You're either captaincy material and someone wants you in that time or you're not."
The captaincy debacle that followed was a sore point not just in McCullum's career but for New Zealand cricket. Taylor got the job but tough times followed, as did talk of disunity and angst among the playing group.
"What that did is it drove a wedge between those who supported Ross and him and those who supported me and myself... within the team and also outside the team," McCullum said.
"It was difficult at the time (getting passed over as captain)... only because I felt I had something to offer. In hindsight I wasn't ready for the captaincy either so in a strange way it's kind of the best thing that could have happened, but it didn't feel like it at that point in time."
There were rumours McCullum wasn't getting on with Taylor, and in 2012 the problems continued when Mike Hesson replaced John Wright as national team coach. Hesson and Taylor's relationship wasn't working and the boss dumped Taylor in favour of McCullum.
"You had to be an idiot not to work out those two weren't getting on ... in the end Mike Hesson decided he wanted to make a change so he axed Ross and installed me as captain."
The now 35-year-old admitted he had to think long and hard about accepting the gig, his wife telling him his only two options were to take on the role in all three formats or retire.
Thankfully for cricket fans, he chose the former.
McCullum retired from international cricket early last year with more than 6000 Test runs and 12 tons in the whites to his name. His record is just as impressive with the colours, scoring five ODI centuries and boasting a strike rate of over 96 across his 260 matches.
Watching him in the Big Bash this summer where he captains the Brisbane Heat, McCullum's attacking instincts have not waned at all in international retirement. He's just as aggressive with the bat and he's constantly changing fields to stay ahead of the game.
Married to an Australian, it's surprising they never claimed him as their own.
