You’re comparing apples with pears. Those other clubs haven’t had huge cash inputs by their owners who’ve then converted the debt to equity. Equity isn’t a loan btw.
The debt is Abramovich’s and will be reflected in the net price he receives as and when he chooses to sell it. If he sold tomorrow for £1BN, then he’d effectively be walking away with a circa £100m loss.
An owner like him calling in Directors loans that a club couldn’t pay would be beyond dumb, as you’d literally bankrupt it, and still not get your investment back. As and when he wants the bulk of his cash back, he’ll sell.
Could he force Chelsea to sell off the stadium and players to get back as much as he can?
