Word is that 'Taker wanted Lesnar to end the streak years ago, and since they are good friends apparently, it was probably an easy decision for him to decide to let Lesnar end it.
Some have said it should have been to an up-and-comer, but I disagree. Sure, it would give a major rub to a possible future star, but what if that guy flames out and never becomes a top star? Then the streak was ended by someone who turned out to not be all that great. It had to end at the hands of someone who is already a top guy, and while Lesnar might be a part-timer, he fits the bill. The other top guy it could have gone to is Cena, but he is already hated by tons of people, and if it had been him to end the streak, my gosh, the backlash would have been unreal.