This doesn’t line up with what is written on his Wikipedia page at all, which claims it was his next novel that was more controversial, and he clearly wasn’t that poor because he did a grand tour of Europe and the Mediterranean a few years after
I can’t speak to the Wikipedia page as I have not read it but the biographical material in my Norton Critical Moby Dick and Delbanco’s Melville line up: Moby Dick was a flop and ruined his reputation in society, Pierre not selling further precipitated the crisis built from choices made while riding a high into The Whale.
Melville bought many things with debt: his farm, his rare books, clothes. I don’t find it unimaginable that he paid for the grand tour with debt spending either.
