Clare said that the Whale knew it was ill, and had come up the river to die. We should have left it in peace.
The official story was that it was confused, and had to be helped to find the sea again (and it was also ill, but then, whale diagnostics are not all they could be).
My view is that it is unlikely that whales don't understand the difference between the sea and rivers. As air-breathing mammals, it's quite likely that if they are sick and in danger of drowning, then seeking to beach themselves on a shallow bank where they could perhaps recover and later re-enter deep water is maybe the kind of last-ditch survival mechanism which evolution favours.
All those people 'helping' were probably the last straw ... but then, they do look a lot like big babies, don't they.