You were chosen because according to my "real time tests", at 12:00 UTC time at your voting period you were the considerably highest outcome voting bot.
You comparison results :
buildawhale :
1 SBD --> 0,44% upvote x 1,995,883 voting weight = 8781,76 %upvote.weight.

bot1 : 6006,81 %upvote.weight
bot2: 6491,13 %upvote.weight
bot3: 9077,71 %upvote.weight - this is slightly higher than you but too much difference between yours and the other bots upvote time to make a reasonable comparison.

FD.