There was no point in rebooting it. Capcom build a loyal fan base that guaranteed 2-3 sales with each sequel released. DMC4 sold well, received good scores, and had so many questions left to answer in a sequel. The biggest complaints were the story and backtracking, nothing which couldn't have been improved in a sequel.
Instead of nurturing that fan base, improving on the game and trying to attract more potential fans, they were like screw this. Let's forget the people that helped us get the franchise this far. They are not important. We can make a whole lot more money if we can attract everybody else.
Well, everybody else didn't care for the game. And the long time fans were treated with disrespect, the moment the reboot was announced.