More likely the water was pumped out when the mine was operating because digging, blasting, and other mining activities are easier when the equipment and people

More likely the water was pumped out when the mine was operating because digging, blasting, and other mining activities are easier when the equipment and people can breathe the atmosphere. I don't know when the pumps were turned off but it would have been after the mine ceased operations, possibly after the owners threatened to walk away completely. Because they could do that in the USA, and many other parts of the world.