If Prithvi wins, then not only is he a friend of the kingdom....but he kinda rules it now.......
Digvijay is similar to rajsuya yagna and ashwamed yagna....both conducted with an intention of establishing an empire....
In Ramayan, Ram conducted the Ashwamed while in Mahabharat, Yuddhister conducted the Rajsuya.....both with the intention of establishing empires..
Prithvi is doing the same thing through digvijay...its a sort of different type of pooja....but with the same purpose as the other two...