There's absolutely money in building a new stadium, take a look at Spurs with their new stadium. Obviously a bigger attendence helps, but I actually think the bigger thing is adding more luxury boxes. I felt like I read somewhere that in the NFL (where they've pretty much mastered making money), the stadium luxury boxes can make as much, if not more, as the ticket sales of general attendance.
Plus you also have to think of it from an investment mindset. A brand new stadium raises the overall valuation of the club. A lot of time you'll get the investors who care more about the overall entity's valuation over profits. Think of it this way, you buy Chelsea for 4 billion, you lose 50 million a year for 10 years making that a loss of 500 mil, but you've increased the valuation in that 10 years to 6 billion, and sell for a 1.5 billion profit. I'm over simplifying obvious but you get the point. A new multipurpose stadium could increase the overall value and at the very least, it's an asset that you can sell to make your money back (although the fans would probably riot).