Often it's because someone has hurt them. Some people become belligerent when they feel inferior to a lot of other people.
https://www.psychologytoday.com/us/blog/passive-aggressive-diaries/201403/7-reasons-why-people-use-passive-aggressive-behavior
What might be a reason for some people to be belligerent?
5 answers
Cause someone is hurt
because stuff can happen in your life
Why is Ms. Sue so smart though? Something about someone hurting them :)
Stuff happens