Is Man Utd's Fernandes issue a symptom or reason for their form?
The interesting bit is that both answers can be true at once. A captain who is visibly frustrated because his team is misfiring can easily make that misfiring worse, and the loop tightens. Fernandes has always played on the edge of rage, and that edge is part of what makes him effective. When results are good, it reads as passion. When they are not, it reads as a problem.
I'd want to see his chance creation numbers and pressing stats before deciding. If those are holding up, then the issue is mostly about goals and assists, which are noisy. If they are dropping too, then the dip is real and the captaincy might be weighing on him. Either way, the framing matters. A team that creates nothing makes its most creative player look finished, and a player who looks finished makes the team look hopeless.
I land somewhere in the middle. Form is contagious in both directions, and United's problems are bigger than one man. But captains absorb the weather, and Fernandes is absorbing a storm. The honest answer is probably that he is both symptom and cause, and the club won't know which until the team around him starts functioning.