It’s entirely rational to think such an expense is unnecessary, especially if your politics inclines you to believe the data collected by these programs will be used to push for more stringent environmental regulation that you dislike.

Even granting that the data is valuable, is it worth $15M per year? Can it be collected privately? Why does the government need to fund it?

To answer your question, yes, people can defend this action rationally. You don’t even have to be MAGA to do it. We should all want more efficient government.