Braided lines with flourocarbon leaders do not stretch (Especially 17lb leader!)hence you could have pulled the hook to a position that "Tore" or widened the hole in the mouth of the fish.

In your case, it sounds like you could have used a lighter leader with mono to "Shock-absorb" the impact of the hookset, or you run the risk of tearing the fishes'lip at the swing.

It was mentioned above that this could have been the case. I'd try a Mono leader in 10-12lb test(P-line flouroclear is a good choice) and will still give you enough strength to land the bigger fish.

Swim's right. Sometimes they just "POP" and there is nothing you can do.

Good luck next time.

"ROD"