This.She didn't fire the band, she fired the bar!
And this!Whatever you do, don't burn any bridges.
As an owner, if a single night's receipts were $10k instead of the customary $3-4k, that would catch my attention and certainly merit investigation. If my manager slaughtered the cash-cow, killed the goose that laid the golden egg, etc. by firing the band. we would have words.
I remember a first outing at one club that wasn't prepared for the size of our crowd. They only had one server scheduled for the night and were scrambling to bring in others once they saw what was happening. Drink service was slow, but we explained it to our crowd during the first set, called out the server by name, and asked everyone to show some patience and tip generously. Man, did that work wonders. The bartender and server loved us for taking the pressure off, and the manager made sure to have more servers scheduled for our show. We gigged there regularly for the next 18 months.