Bismarck found the Guelph funds- the sequestered estate of the Hanoverian monarchs- extremely useful in bribing individuals from journalists to the King of Bavaria. With a pro-Prussian Hanover, domestic politics could be a lot more awkward. Incidentally, an interesting POD to establish this comes from Bismarck's autobiography:
"In September 1853 the prospect was open to me of becoming a minister of state in Hanover. Just after I had gone through a cure at the baths at Norderney, I was sounded by Bacmeister, who had just retired from Scheie's ministry, as to whether I would be a minister of King George. I expressed myself to the effect that I could only serve in the foreign policy of Hanover if the King was willing to go completely hand in hand with Prussia. I could not take off my ' Prussianity ' like a coat..."