Melville was a prominent author, an early sex symbol even, owing to the success and popularity of his novels before Moby Dick. That novel was hugely controversial in its day -- perceived as blasphemous, overwrought -- and it ruined his reputation as an author. Also, he'd spent money he didn't really have during the writing of Moby Dick so that when it flopped he couldn't survive on the famine part of the feast/famine divide.
Point being, had Melville continued writing south pacific adventure novels he probably would not be remembered today but might have died a well-off man.
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.
Point being, had Melville continued writing south pacific adventure novels he probably would not be remembered today but might have died a well-off man.