http://www.revivingthestrike.org/ in this book, the author claims the purging of union militants through 'loyalty oaths' during the cold war, passage of Taft-Hartley laws that banned solidarity strikes, essentially changed the way workers think of themselves and union officers think of unions. A change in status from embattled union activist to powerful head of trade organizations can also make people more open to negotiation and compromise rather risk everything on a head on conflict with management.