I don't wish the guys memory any ill - hell, I'm an admirer of his work - but his dismissal from Iron Maiden was down to him and him alone.
Not only that, Iron Maiden went on to great commercial success due to Nunber of the Beast, a new sound only made possible by Dickinson's voice, vocal skills and work ethic, all of which enabled Harris to write the more technically demanding songs he'd wanted to do for a while. That Dickinson had to that point never had any vocal coaching made his performances and abilities all the more remarkable.
If Di'Anno had instead hypothetically continued with the band they'd have probably done OK but are unlikely to have hit the stratospheric heights that the band was later to reach with Dickinson.
So the Mail's quite frankly nasty story was based on a speculative future which almost certainly could never have been.
Even if he had remained with Iron Maiden it's unlikely he'd have been financially a great deal better off that he was, and his band mates would never have enjoyed the huge financial success they earned with Dickinson. It is what it is, not what it could never have been.