It doesn't have to be one or the other, I for instance feel every sympathy for both Liam and Maya for very different reasons, just as I feel every sympathy for Kate, Cheryl and their son, his family, his 1D band mates, all for vastly different reasons.
Just taking Liam and Maya into account for example, I feel an immense amount of sympathy for them both, whatever happened between them.
They clearly loved each other at one point, and if reporting is true, they remained in some sort of contact during what would end up being his final months, on whatever basis that was is up for debate.
Neither of them expected him to die, at least not in the way he did.
Whether it was one or the other, or both of them, it's possible to feel very sorry for both of them, let alone everyone else involved in what's turned out to be a very sad story to a young boys life who once had so much promise.