The telescope is studying the sun. Solar events have non negligible effects of the weather. Mauna Loa produces meteorological reports used by sailors and pilots all around the world daily.

This observatory is the first one to show CO2 concentrations in the atmosphere, and their analyses have been cornerstone to the climate discussion since it's inception.

Unless it's shown that the observatory is burning millions, it's nonsensical to shut it down. It's not free to set up another equivalent lab.

And locations similar to Mauna Loa are not very common, to be clear. It's not gonna be cheaper to set up an equivalent.