Imagine that every person who had gone on to do something extraordinary in a field of endeavor had had a shared experience --
E.g. imagine that every scientist who received the Nobel prize in 2015 had coincidentally been at the same summer camp in 1995 and seen a person give an amazing talk that inspired them all to be scientists. Or imagine all of the great musicians of the 1970s had been to Woodstock as teenagers.
What would you call this shared thing?
Bonus points: I'd love if there were also a sense in this phrase/word of a "crossroads" - that is, there was directionlessness and this event "cleared the way"