Did i make a mistake?

or just stay away from tournaments with rebuys?

https://www.replaypoker.com/hand/replay/496459837/flush-ace-high

Not really, your bet was right, but the winner did have both the table chip lead and a four-card straight flush draw. So, he could get lucky and kill you, while the best you could do was to cripple him. It isn’t shocking he called.