The $1 billion sale of Detroit's Greektown Casino-Hotel is the culmination of several factors, including industry trends and timing.

First, and perhaps most simple is basic economics: Greektown owner Dan Gilbert wants out of the casino business, and found buyers willing to pay an agreeable price.

The buyers — Wyomissing, Pa.-based gaming conglomerate Penn National Gaming Inc. and New York City-based Vici Properties Inc. — like Detroit because Greektown is a mature property with a known track record in a market where competition is limited and stable. State law permits only three commercial casino licenses in the city, which has been experiencing a downtown investment boom.

Big Las Vegas-style casinos are rare in the downtowns of major American cities. Most casinos are on the outskirts, in suburbs, or far-flung locations away from major population centers.

Not Greektown's 400-room hotel and casino, which is among the reasons why Penn National has pursued it for years.

"It represents an opportunity for the company to expand and diversify further in a great market with a property that is ideally situated. The acquisition will also be additive to Penn National's operating results," said Penn National spokesman Joseph Jaffoni. He said Detroit is ideal because of the city's "improving economics."

Gilbert is widely credited for creating a share of those improving economics after moving his Quicken Loans Inc. and thousands of workers downtown and then acquiring, renovating, and filling more than 90 downtown properties. He bought Greektown, part of his Jack Entertainment gaming properties, for what he told Crain's was approximately $600 million in 2013.