The OED has not caught up with this development, but MWC10 gives "a person or thing that inspires legends" as one definition of "legend", and "well-known, famous" as one definition of "legendary". There is nothing out of the ordinary in such a usage, but it is a fad, and I find it tiresome. When large numbers of people start using a word on every possible occasion, IMO, sensible people stay away from it. So also for the faddish uses of define, impact, reinvent, identity, etc., etc.