Why do you think it took so long for the workers to stop the flow of oil from the underground well?

The correct answer is due to the phenomenon known as a blowout.

A blowout refers to the uncontrolled discharge of natural gas and/or crude oil from the gas well or oil well after pressure control systems have failed. The contemporary wells exhibit blowout preventers, which are aimed to inhibit such happenings.

Before the start of the pressure control equipment in the 1920s, the uncontrolled discharge of gas and oil from a well while drilling was usual and was called oil gusher or wild well.