It's not Yakuza's studio, it's the new independent startup founded by one of the creators of the Yakuza series.
Reading a bit into it, it just seems like financial mismanagement sussed out by the investors, who then refused to invest any more. I think Nagoshi sold them a bill of goods that he couldn't deliver at that price and wanted a AAA budget for a AA or indie game.
Remember, as great as the modern yakuza's are, they were built on the backs of all the previous yakuza's, reusing tons of assets and minigames. Without those resources, having to build everything from scratch, Nagoshi probably vastly underestimated what he would need to build a polished game.