Mike wrote:

What is it meant to commemorate? The fact that he failed or the fact
that he tried?

Failed, I believe - hence why you burn the Guy on the bonfire, not some
effigy of the Government.

I suspect the reason might be that Bonfire Night, traditionally, is a
family celebration and will tend to be over with earlier on anyway,
with those messing with fireworks later on probably just causing
trouble.

Neil