He didn't wear a mask or socially distance. That's irresponsible as if he was infected, he could pass the virus on to others. Not talking laws here, just health guidelines that he's well aware of (the fact he had a mask but was wearing it below his face shows masks were being worn there).
The fact that he has tested positive means he caught the virus before, during, or after the wedding. If it was before, it means his actions could have spread the virus to others - irresponsible. If he caught it at the wedding, then his actions could have certainly contributed to him catching it. If he caught the virus after the wedding, then what was he doing and was he following the guidelines as to how to reduce the chance of infection?
Mo's a great player, and a great human being. But he made a mistake here and was a bit of a silly boy. Thankfully, he seems to be in good health, and hopefully the same is true with anyone he came into contact with subsequently.
He didn't do a Kyle Walker, but I'm sure the Liverpool management will be a little upset with him. Line drawn underneath it, moving on.