A vanguard is different from a leadership, even in metaphor (if you can excuse the military metaphor). It exists only because it’s at the front – if the direction changes, the vanguard changes. Whoever catches up to the vanguard – no matter how many – becomes the vanguard. If no one follows the vanguard, it ceases to be one.
For socialism-from-above, leadership and vanguard are the same – either something to be, or to resist, or that they already are.