Is there a reason for the "need" to move tumblr over to wordpress? As noted tumblr isn't profitable, why expend all that effort and cycles if being on a differ

Is there a reason for the "need" to move tumblr over to wordpress? As noted tumblr isn't profitable, why expend all that effort and cycles if being on a different back end doesn't change the nature of the product's profitability? Sounds on the surface like a very engineer type decision where "it would be better on this technical X" doesn't really change the business at all...