They weren’t telling people not ti wear masks they were telling people that they didn’t need to wear them and had no effect. He made groundless statements because they wanted to ensure there was enough supply for healthcare workers. Then they started saying that they actually work and we must wear them.
Personally I do think they can help. But the government has been consistently dishonest. It’s not difficult to see how people won’t believe a known liar.
EDIT: for those that have a hard time accepting facts. here is a video that quotes fauci then an now confirming my points www.youtube.com/watch?v=l5FY58I5RQ0