I got Colwyn Bay, which as a town has a population of 30000, from Blue Square South to Premiership. When I got there they built me a 15,000 seater stadium. It's very hard to maintain good finances as gate receipts are so low, but managed to cope by signing young players and selling them a few years on. After a few years, built a decent squad and won the league a few times. Managed to win the Champions League a couple of times too. Currently, I am the 5th biggest club in the world which is good considering I still have a 15,000 seater! The downside of having a stadium built is that you have to wait 20 YEARS before they will build a new one. SO, after 20 years of premiership football, the board have agreed to build a 62,000 seater! Its also worth noting that I had around 50m in the bank (the board were offering me 250m transfer budget a year, which I hardly spent any to keep finances good!
I think its more to do with club reputation and money in the bank