I saw this when it first went up--which motivated me to research the warrior queen. Quite a story, no question. The consensus seems to be that she suffered from overconfidence (she and her army had destroyed towns and beaten Roman soldiers before) and poor battlefield strategic abilities. She no doubt was an effective and charismatic leader who underestimated the well-drilled, professional Roman Army.
Mead.
The Romans didn't generally wall their cities until the 3rd century, and even colony towns were often unfortified. Boadicea destroyed undefended towns and mostly slaughtered defenseless civilians. When it came time to overwhelm a much smaller Roman force, pllllt, she was gone.
I really enjoyed reading Caesar's Commentaries on the Gallic Wars years ago, particularly the last book in which Vercingetorix was surrounded with a good sized force on a hilltop fort; Caesar built pallisades all the way around it, and knowing that all of Gaul was on its way to relieve Vercingetorix, built another set of pallisades on the outside, a sort of doughnut. That guy sure had a set of stones. ;')
Most of the people the Romans were up against simply didn't who they were dealing with.
You couldn't pick up a book in Ancient Britain about the size of the ROman Empire, its operating techniques, etc.
She was out to revenge an unspeakable and stupid outrage against herself and her people.
If I remember correctly, Paulinus was later recalled and the Romans tried to be more conciliatory instead of predatory.