"Why did Jesus choose the 12?"
He couldn't help it, His Father told Him to.
Jhn 17:5 "And now, O Father, glorify thou me with thine own self with the glory which I had with thee before the world was. I have manifested thy name unto the men which thou gavest me out of the world: thine they were, and thou gavest them me; and they have kept thy word. Now they have known that all things whatsoever thou hast given me are of thee. For I have given unto them the words which thou gavest me; and they have received [them], and have known surely that I came out from thee, and they have believed that thou didst send me.
Jhn 17:9 I pray for them: I pray not for the world, but for them which thou hast given me; for they are thine. And all mine are thine, and thine are mine; and I am glorified in them."
Ok... Why did His Father tell Jesus to choose the 12?