He was mostly lucky in that regard. The amount of fires Barnum had with only animals dying and not people is pretty impressive. He had at least five buildings burn down alone. One of his fires at the American museum had a nice effect due to the cold weather in New York at the time.
It took a while after his death before one of the big top shows really went up in smoke with significant loss of life.
If I’ve learned anything from your elaboration, it’s that I should vote for an arsonist, but only if they burn things for insurance money rather than murder.
On a more serious note, the first fire alarm boxes weren’t invented until Barnum was 42, and still took some time to spread from Boston. Places weren’t super-well equipped to deal with normal fires, much less ones that started in places filled with hay, dust, paint, paper, and dyed cloth.
