As it turns out, it wasn’t a well-equipped, scrappy, passionate rebel alliance that brought down the Galactic Empire.  It was poor planning (why wasn’t there a backup to the shield generator on Endor?), bad design (an unprotected thermal exhaust port that leads directly down into the main reactor – twice?), arrogant leadership (don’t need the Imperial Guard around while the kid who blew up the first Death Star is in front of me, along with his pissed-off father whose loyalty I sometimes doubt), unquestioned assumptions (just lure the entire rebel fleet into a trap with a new Death Star they think doesn’t work – what could go wrong?).

So lots of holes enabled the compeition to hand them their collective Imperial asses.  These and other flaws are described here.