He said in an interview that the decision wasn't really hard. Tottenham have ambition to go back in the CL and stay there. Their style of play was important, that they played good football. He also said that having Lennon and Bale on the wings suits him very well and that Bale signed an extension helped out. Also that they have brand new training facilities that will be finished in a months time.
The way he talked seems to me that it hardly mattered at all that Rodgers was the manager at Liverpool. Squad, style of play in previous seasons, how they've done in the league. All factors in. Maybe as well the fact that he's a United fan but he'll probably never say that on the record.
Will be interesting to see if AVB will play both him and VDV together somehow. Wouldn't think so.