Not for lack of trying, mind you. Previous attempts were eventually thwarted after decade-long efforts, which is also how this one looks like it’s shaping up. It’s also worth pointing out that in previous cases there were champions of the industry that stood up for Linux and countered with equal amounts of money into things like lawsuits and marketing on the supporting side. Furthermore this attack is of the FUD variety (fear, uncertainty and doubt) which is harder to counter.