the grand tournaments where for hardcore players who scored really high
the rewards are only based on ranking so with just 12 k points you failed to win a spot and thus did not receive rewards
check normal tournaments your 12 k points will be rewarded for
the grand tournaments did not include normal rewards ( units/ resources/ boosts/ keys,,,,,,,etc)
the only reward was sapphires
finally rewards are completely based on ranking (no matter what points you have collected you will only be rewarded if you won a spot)
note:- the current grand exp tournament is different you will win rewards if you earn 70k points even if you do not win a spot in rankinghope this helps