Don't understand something at the end (spoiler)
When Sarah died Eddie and Bert have an altercation which in my mind leads me to assume that their professional relationship is over. This is even more reinforced when Eddie returns to challenge Fats in their rematch because clearly there is animosity between the two characters. Eddie challenges Fats and puts up his own stake (zero input from Bert) and then out of nowhere Bert demands a cut of his earnings at the end.
Isn't a sponsorship/staking agreement dependent on them actually backing you? Otherwise Bert could take zero risk (put up no funds) but then just take up a cut of Eddies winnings.
Did anyone feel the same way or have an explanation