The first and foremost reason is that it is the biggest fight that can be made right now in boxing from an attention to the sport and financial viewpoint (forget Manny, that can't be done, he has all his next 3 fights with TR).
The second reason is that Canelo may be big enough and strong enough to make it interesting, which currently no 40 or 47 pounder can claim except maybe Khan and Petersen who could have some success with things they do.
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