The notion that all bullies are actually cowards who are all bluster and will run away as soon as some courageous person stands up to them is a trope that really needs to be retired.
We’ve all seen this a billion times in movies and TV shows, and no wonder! It’s wish fulfillment. Who wouldn’t like to believe that the kid who makes our life hell every day at school will fold as soon someone punches back, or calls them out in front of the crowd?
This fiction also tends to be pushed by parents and other well-intentioned adult authority figures. Wishful thinking here as well.
The problem is that most bullies are not cowards. Most bullies are assholes.