She discovered, wrote, and established a philosophy of individual, social, and economic life. She produced a literature of enlightenment to the benighted, an illumination of the nature of evil in contemporary society. For tens of millions she has provided a foundation of learning that influenced and informed their lives (e.g. Greenspan, Ryan, etc.) and like Friedman and Buckley she was a crucial counter-weight to the overwhelmingly liberal zeitgeist of the 60s and early 70s.
She was for youthful millions the first opportunity to break free of mind deadening liberalism - and the enormous antipathy to her legacy is a marker of her success.
She was one of a string of ideologues of the late 19th and early 20th centuries, each of whom was convinced that their new philosophy could lead to utopia, if only the rest of the world would fall into line.
Fortunately, her Objectivism was never attempted as a guiding principle for a nation state; other contemporary ideas were, unfortunately, less comprehensively disdained - Soviet and Chinese Communism; National Socialism; Spanish and Italian flavours of Fascism; Japanese Military Imperialism; South African Apartheid - every one of these ideologies generated by the navel gazing of self-appointed philosophical geniuses that was actually tried, ended in disaster. There is no reason to imagine that those (like Objectivism) that were not tried would have been any more successful.
All of these ideologues - Marx, Lenin, Stalin, Trotsky, Mao, Pot, Hitler, Franco, Mussolini, Tojo, Smuts, Rand, and dozens of others, had devoted followings - and most still have devotees today, any of whom, if asked, will tell you that their chosen demagogue, unique (or at least rare) amongst all of mankind, "produced a literature of enlightenment to the benighted, an illumination of the nature of evil in contemporary society. For tens of millions (s)he has provided a foundation of learning that influenced and informed their lives" - or some similarly pathetic gushing hagiography that bears little relationship to observed reality.
All of these utopian dreamers were badly wrong; but that didn't mean that they were not dangerous then, nor that they cannot become dangerous again, if we allow hero-worship and piss-poor philosophising to replace humanity and freethought.
If we accept that "enormous antipathy to [a person's] legacy is a marker of [their] success", then we must conclude that Hitler and Stalin were amongst the most successful political philosophers of recent memory.