I think you are just fundamentally confused. There are two separate entities with similar names. There's the Mauna Loa Observatory, which is what's being discussed here, and there are the Mauna Kea Observatories. The latter one has the telescopes. The Mauna Loa Observatory monitors the atmosphere. It has other types of sensors that are useful for atmospheric science. It isn't an astronomical observatory that just happens to have a CO2 sensor. It was specifically set up in the 1950s to study the atmosphere because of the advantages of being at that specific location. It just happens to have a name that's similar to an institution that does have telescopes.

Perhaps you should have some basic familiarity with what they do before deciding that they shouldn't be doing it. https://gml.noaa.gov/obop/mlo/programs/programs.html