Right, but there's not going to be one solution to "diseases caused by aging". If you spend 5 years exclusively trying to rejuvenate a dog, and you actually succeed, are you really better off than if you had spent that time and money exploring a number of strategies and using existing research infrastructure?
I mean if somebody theorized a single device that might cure aging, then the Manhattan Project might be a good model. But nobody even knows what the goals should be, what projects will work, what areas should be studied. We don't know enough to start a singularly focused project.
http://santafejeeptours.com/wp-content/uploads/2015/09/Santa... (from the TV show "Manhattan")