Even if "only" 25,000 people go to 17 regular season matches a year (not counting potential concerts, other uses, etc.) it would still potentially benefit the city greatly. There's the hundreds of construction jobs for a year or two, there's the material suppliers (concrete, steel, glass, etc.), there's the employees (vendors, concessions, etc.), taxes paid to the city, and probably a ton of other things I'm not thinking of off the top of my head. What about the income from a number of World Cup matches at some point in the future, for example, or college matches (not counting other sports besides soccer).
A good stadium in a good location could definitely greatly benefit the whole city, not just the fans who would go to matches.
Whether the oil tycoon could pay for it 10 times over is of course a separate discussion.