The only thing this proves, is the sheer degree of irregularity that has to occur so that my words can be half-mocked after some very diligent research on your part.
It's just the odd, but perfectly rational "mistake" in an ocean of level-headed and often precise assessments.
Aren't there limits to payout sums? Usually there are. In any case, the amount of money people have placed on Chelsea/City/United/Arsenal/Liverpool for winning the league (and will be kept by booking agencies in the case of a Leicester victory) should definitely outweigh the amount of money that said bookies will have to pay out.
edit: Now both Arsenal & Leicester are at 9/4, City 7/2 and Spurs 5/1.
Just saw it again. Several ligaments are probably teared. More than one would be my guess. His entire leg bent backwards. Note a bone fracture, but the knee is seriously damaged. I'd say it's a 6-8 months injury based on the replay.