Not everyone obeyed the ban, with some making a fortune in the process.
James DeWolf, Senator, wealthy RI merchant, and local philanthropist, continued engaging in the slave trade for decades and through it amassed one of the largest fortunes in the US, at the time. It should be noted that by the end of the legal trade the DeWolf family had already been engaged in slave trading for decades. But it was under Senator DeWolf that the family decided to forge ahead despite the legal prohibition.
The trade also indirectly fueled local RI business, like smiths who made the shackles used by DeWolf slavers.
A great PBS documentary was made about the DeWolf's role in the trade called Traces of the Trade. I highly recommend it.