They still sold millions of minis. Can't sell is about relative terms to the rest of their iphone sales. Against that it looks poor. Against mac pro sales probably looks amazing. Sold by any other company the phone would probably be considered a success and still in the lineup.
And really, poor sales are no excuse. How many macbook skus do they have that barely move when you go through all the permutations of config? I don't want to work it out but I'd guess there are something like 24 skus of macbook pro they are barely selling in comparison to iphone sales. What's another model iphone in 3 storage tiers?
Another phone model is massively more expensive compared to changing RAM or storage in, say, the macbook lineup.