Newspapers do not instruct the views of their readers. They chase them.
They chase the views of that section of the populace they’re trying to appeal to that is. So, the FT is soft left europhile because that’s the profile of those likely to read the FT.
The Sun is aiming rather more for the gut of the working classes. Sure, they don’t always get that right (Hillsborough anyone?). But that they’ve called it for Leave by calling for Leave is an interesting indication.
Remember: they’re trying to work out what their readers already believe then say that, just like any good salesman does.