its because they at first made things overly vauge (the first vote) then the MCYT memed the glow squid to basically force it to win when mojang didnt want it to (they planned to add the iceologer, but couldnt because they didnt want people to get mad, they were mad anyway) then they did something right and made all 3 mobs viable options (allay won) then they somewhat manipulated the mob vote to get us to add the sniffer (they made it seem like it would give us seeds that made new crops, aka a farming update, instead we got a cute mob and a couple of random flowers that do nothing)
in short, mojang has made multiple mistakes, be it being too vauge, letting outside forces manipulate the vote, before doing something right and immediately backtracking to self manipulate the vote.