Why did many Hong Kong people emigrate before 1997?

I remember that in the early days of reform and opening up, Hong Kong people looked down on mainlanders, and rumors about how poor and backward the mainland was flooded the streets. Even though the return of Hong Kong in 1997 is irreversible, the future of Hong Kong after the return has always been a topic of endless debate. So many Hong Kong people choose to emigrate before 1997.

However, with the strong national strength and economic development level of the motherland.