It's really that the PSP was a failed system at this point. DXC wasn't the only one that didn't do well. it's just about any PSP game. Developers tried to make block busters for a system that has been hacked to hell and back, and had a smaller market share than its weaker competitor. Companies like Capcom and Konami pumped in some serious money into some of these games to see poor returns, thus abandoning the system in some ways and put partial blame on the series the game was from and or the style of game it was.
Bottom line: Companies placed undue blame on the game/genre, instead of blaming the medium. Had Maverick Hunter X, Megaman Powered Up, and DXC been on the Wii instead, they would have made a hell of a lot more money.