Why Did Some Indian Princely States Join the Union on Such Different Terms?

I’m trying to understand the political choices made by princely states during the transition to independence. Some joined the Indian Union quickly, while cases such as Hyderabad, Junagadh, and Kashmir followed very different paths.

Which factors mattered most in each case: the ruler’s decision, the population’s preferences, geography, or pressure from the new governments? I’m particularly interested in how historians explain the accession of princely states without treating every case as if it followed the same script.