Anyways, hadn't Hussain been considered a very strong candidate early on in this thread? Hmmm...
I think it's impossible to know what really happened unless you're from Bradford, which I'm not. But I can make some observations.
There certainly were comments from some quarters that Hussain was a strong candidate, but parties always claim things like that. I'm not sure that I saw anyone I'd consider neutral saying it.
I think his status on the Council may have harmed him. Bradford has fairly major problems at the moment -- in particular there's an infamous "hole" in the city centre where buildings have been demolished to make way for a never-built shopping centre -- and some of the stuff about this by-election, and some of what I've seen on the local news, suggests that some of the dissatisfaction which led to this result was connected to that.
If this is right, then the local elections could be very ...um... interesting.
Then there's the whole biraderi thing. Some reports suggest that there was a bit of a rebellion in the Asian community against it, and Hussain suffered from that. (This may be related to the above.)
