Contingency theories are a class of behavioral theory that contend that there is no one best way of leading and that a leadership style that is effective in some situations may not be successful in others.
An effect of this is that leaders who are very effective at one place and time may become unsuccessful either when transplanted to another situation or when the factors around them change.
This helps to explain how some leaders who seem for a while to have the 'Midas touch' suddenly appear to go off the boil and make very unsuccessful decisions.