It's all RNG. I have noticed though that on several occasions, and not just myself but people I grouped with and fished together with, got two of the same same fish in quick succession. I found I got several hats, while chasing the +5 line while my friend caught two +5 lines and still does not have a hat. I don't think what you want has any impact on what you catch, I only mention it for the amusement factor.
I have caught four rares in a single tournament and zero in others. That's just how it works sometimes. Don't give up. You'll get it if you keep trying.