They are not fighting to “keep” anything because it was something that they never had it to begin with.
Certain elements in society (mainly university students and young people) have it in their minds that China has reneged on its promise to maintain a high degree of autonomy within the one country, two systems principle because it is not allowing individual Hong Kong citizens (instead of a 1200-member electoral college) to nominate candidates for appointment as Chief Executive.
It can be speculated that the people who are inciting the students and young people to protest are populist politicians who would like to be Chief Executive themselves, but who stand no chance of being nominated by the Electoral College.
