I guess MS made them an offer they couldn't refuse? </said with an attempted Italian accent for a bit of humour>
Maybe, but that would have to be quite a bit. Assuming this exclusive does a best case scenario of matching Uncharted numbers, thats 4-5 million copies. It took ps3, 360, pc, xb1 and ps4 for TR to hit 6 mil. I would think they would have to match that at a minimum for it to be worth Square's while.