Hidden attribute in players is well proven in the way that player form is consistant with that in effect.
Hidden attribute also decides the training efficiency and market value of a player, especially the market value is not random but a calculated value given from the hidden attributes.
The real question is, how many hidden attributes are there?
Maybe, every ability skill of the player gets its own bar just like the morale, so that a low "fitness" player become more prone to injury just because his current state say so.
Anyway, all strikers down is not that unusual even on pure random perspective. The chance of it happening isn't zero and people will have it sooner or later. If it is not the strikers it could be other positions so the chance of that stacking up isn't as low as you thought.