In reality it was about mix of reasons, main ones was, first, HK was choke full of various crooks who would had chance to move to slammer under Chinese law so they shat their pants, and since they were influental there they incited the petty burgie mob going hard on red scare, commies confiscating their toothbrush etc. Second main reason is because the new law was a step towards decolonisation from British colonial and financial power and this moved the really big players to support the former two levels.