They never really expanded close to enough. People didn't want to be roaming when they went to the cottage or camping or whatever and even then the urban areas served were still too concentrated and small.
I think had they focused on southern Ontario or BC and expanded from there rather than aiming to hit the all the big metros first they might have done better.
Decisions are made at the margins. It’s always possible to look back and say “they should have done X, and they would have succeed.” It possible that there were many factors, but in my mind no minor change to the strategy would have helped. Had they done what you suggest, I’m sure the respond would have been that they targeted too small a market, or they didn’t cater to folks traveling between major cities frequently.
IIRC Wind was offering unlimited plans at 50% the price of a mediocre plan on major providers. You could have hours of roaming calls and still come out ahead (and this is in the edge case, where you happen to go camping that month). Most things being equal, Canadians broadly prefer to pay more to have a sure thing. It’s not a bad instinct, but it has consequences to how industry is shaped in the long term.
I think had they focused on southern Ontario or BC and expanded from there rather than aiming to hit the all the big metros first they might have done better.