Yeah, this is a common entrepreneur failure mode. You need to be ambitious and visionary to start a new thing. And investors love to hear the grand plans! Tempering that is one whole other skill.
That guy sounds like he was trouble from the beginning. But if you get in this situation again with somebody less crazy, one thing I've done is to draw a graph with a dot just above the zero point and then a circle at the top right. I get them to talk about their grand 20-year vision, and I explain that's the circle in the upper right.
Then I draw a bunch of tiny line segments that walk erratically toward the circle. I explain that each week we need to take one step in the direction of the vision. The I ask them to focus real small, and think of the tiniest thing we can do toward the goal, something that fits in a week. Once the have a few of those, I'll ask, "How can we prove that this step really went in the right direction?" (It can also be useful to pull in the Lean Startup framework of validating hypotheses here.)
Sometimes that's enough to get visionaries to start breaking it down. And sometimes it exposes that the person is only good at dreaming big, but is unable to actually execute. Either way, it can yield valuable info.