I don't know. For one thing, it means they trust Rusev to take Taker's stuff and MAYBE get some in on himself. They also trust him to work a convoluted match like a Casket Match. They see him as big enough, relative to their other options, to stand with Taker in a featured spot to a degree. I imagine if he has to travel all the way there, he'd much rather be in this match than just be in the Royal Rumble, payday aside. Plus, you know he and English are going to have a lot of fun with promos and things to build it up.