It comes down to this: the new owners needed to remove the signs (since it's no longer the Trump Taj Majal) and hired a company to remove the signs and send them to a landfill. An employee of the removal company sold the signs (likely on the sly) to someone who put them on Ebay. The casino's new owners halted the auction, so the buyer of the signs has sued, saying they bought them fair and square and the casino owner can't stop them from reselling. They also say the signs have increased value as a casino collectible or as a presidential collectible related to a failed Trump business.

I could create version that uses a lot of abbreviations for all the companies involved, but that would be cruel.