Personally I'm not particularly worried for the club at the moment - he has well over 100m in the club, he is obviously a serious investor.
The sums do become baffling though - why would he want to spend 500m on players to try and increase his (sic) ~100m by a modest amount ? Of course he can only do that because the cost of the players is against the club debt, not himself.
So, when we throw 50m away on a crap player + saddle the club with his millions in wages for 5 years - it does concern me, and it should concern fans - because that debt is the clubs - it is not free money from Moshiri.
If Usmanov helps the clubs income by sponsoring - or if Moshiri puts his own money in or buys more shares - that shows real investment - borrowing against the club does not.
(I should say, I don't know how money Moshiri has leant the club himself .. would be an interesting stat).