Why was it necessary for Marshall to take the trouble to explain why navigation should be considered part of commerce?

Marshall needed to explain why navigation should be considered part of commerce to establish a legal framework that recognized the interconnectedness of trade and transportation. By doing so, he aimed to ensure that navigation was protected under commerce regulations, thereby facilitating economic growth and development. This explanation was crucial for clarifying jurisdictional authority and promoting a unified understanding of commerce that included all aspects of trade, including maritime activities. Ultimately, it reinforced the importance of a comprehensive approach to economic activities in the legal system.