I don't think there need be any mystery as to why Mulcair didn't have a wider organization in place, especially outside of Quebec. It comes down to four things.
1. From the day he was elected in the Outremont byelection until May 2, Mulcair had a different job to focus on. Unless his personal leadership in Quebec produced some results, there was no point looking a the national leadership. And for some time after May 2, he was working on ensuring that the new Quebec MPs (in particular the "accidental" MPs like REB) got some solid mentoring and no small amount of handholding.
2. He thought he'd have at least some more time - like at least a year.
3. Any post-Layton leadership planning he did would (if discovered) run the risk of being spun as an attempt to undermine Layton.
4. Mulcair likely expected that HE would be the establishment candidate. I certainly did.
I think those are all pretty valid points. I for one was very surprised the way the Brian Topp leadership bid was launched so suddenly after Jack Layton's sudden death. (At least Jack Layton's death seemed very sudden to the general public. Maybe the caucus and NDP staff had more knowledge about Jack's health).
I'm curious if anyone can remember if there have been any provincial NDP leadership contests where an unelected party staffer or organizer became leader? Actually, just asking the question, I am thinking there might be at least one situation where an organizer/staff member was elected leader. I'm thinking of Grant Notley, a former leader of the Alberta NDP. I believe he was a party organizer before he was elected leader of the Alberta NDP in 1968. But Grant had run twice for the NDP (1963 and 1968). And the other obvious point is that at the time, the Alberta NDP had no elected MLAs.
I am glad that the NDP will have a fairly long leadership campaign as it will give the members more time to evaluate the different candidates. This should also provide a good opportunity to build party membership, especially in those provinces where the membership numbers are weak (such as Quebec).