As I understand Fawkes was a fairly minor part in the whole thing, so when/why did the 5th November become known as Guy Fawkes Night, rather than, say, Robert Catesby Night?
I'm certainly on expert on this topic at all but I do remember watching snippets of Channel 5's The Last Days of Guy Fawkes when it aired (you can watch it here) from what I remember of it, it walks the audience through Fawkes's first meeting with Catesby & the other plotters in the Duck & Drake Pub on 20th May 1604 (roughly 18 months before the fateful night) right up until Fawkes's execution on 31st January 1606 (roughly 20 months after the plot was planned).
It explains how Fawkes was betrayed by the other plotters & therefore the most infamous out of the plotters. For books on the subject I recommend James Sharpe's Remember, Remember the Fifth of November: Guy Fawkes and the Gunpowder Plot & Antonia Fraser's Faith and Treason: The Story of the Gunpowder Plot
Hopefully this helped a little :)
I'd think part of the reason is that Guy Fawkes was the conspirators' explosives expert. Not only was he the first caught, but he was the one who actually knew how to make the plot work.