Affordability and profit are two separate measures (over the short term).So having taken on £637 million of debt directly to pay for the stadium it should've been fine to take on an extra £100 to £200 million of debt to overhaul the playing squad? Or alternatively taken on £800+ million of debt for the stadium (fine as it is a long life asset) and used the football club generated profits for player spending as we tended to do before embarking on the capital project?
The club could have easily borrowed a few £00M more if needed, I'm sure. On infrastructure projects that's an easy choice to make as they'll almost certainly make their money back (plus a return) over the period. I don't think there was a problem with affordability.
But eventually those books have to balance. We have to get value for our purchases and we can't just stockpile players who aren't good enough. We have to be sure the player's we're buying are right. After a period of rapid price inflation, player prices appear to have settled again - we can now go into the market a little more certain than we were at the time.