Probably because it's time to win. Honestly, I was one of Collins' few backers last year when times got tough, but if Collins sucks this year again, the Sox not only won't be able to use him as a decent chip in a trade package but will once again have a hole at DH. In today's game, it's relatively easy or at least should be relatively easy to find a DH who can get you 30+ homers which is exactly what Encarnacion can do.
Also, what does pedigree even mean? All of these guys are accomplished or they wouldn't in the majors.