For the league, of course they can't credit you the money for 1st place straight away. Let's say you're top of the league on goal difference after 25 matches, then you win your final match by a narrow margin, but 2nd place goes on to win theirs by a large margin and beats your goal difference, thus taking 1st place from you. If they had credited you the money after your final match, they would have had to take it back or something.
For the CL final, once you win the final, you've won it, so I'd expect the money straight away. It's also possible that you only get it at the season update, though, to make things easier.