From the same article: If that testing shows the virus has slipped into the country in places federal officials don't know about, "we've got a problem," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told USA TODAY's Editorial Board Monday.
So when the situation changed, his view also changed.
Yeah because he knew that there was a supply crunch at the time and wanted them to go to first responders. Morever there is not solid evidence that mandatory masks are necessary, as Singapore hasn't mandated them, and amidst other social distancing procedures and testing regime, they have kept numbers relatively low.
So when the situation changed, his view also changed.