What is it about Locke's philosophy and how people went about implementing it that enabled the revolutionary liberal states to maintain power when all of the socialist states from the 20th century revolutions have more or less faltered or converted to a capitalist mode of production?
I'm...not sure your initial premise is entirely accurate. Liberal democracies have fallen with regularity since the Enlightenment. France, the birthplace of the Enlightenment, has had shall we say numerous different attempts at a liberal democratic government. Germany, Italy and Japan, to varying extents, were liberal (or liberalizing) prior to the rise of fascism. Failed democracies are all over Africa, the Middle East, and Central/South America. And so on.
Meanwhile, socialism (in its democratic form) is alive and thriving in many countries, and single party (Marxist-Leninist) socialism still exists to varying degrees in China, Vietnam, Laos, and Cuba.
None of this is to add any value judgment to any particular system, just that you might want to revise your premise if you want a useful answer.