The claim is that the letter was cc'd to multiple recipients and consequently went viral even before the Navy Secretary had seen it. I could understand that being unacceptable to the chain of command.
Simultaneously, there is no question that this broad distribution compelled immediate action, which may have helped prevent a much larger outbreak,
Social distancing is impossible aboard a carrier, a 100,000 ton ship with 4-5000 sailors and airmen aboard. Hopefully the Navy will recognize that the breach of protocol prevented what could have become a major problem.