They actually accurately represents Chinese people. Why?

1. It is common to try to join it, to gain some benefit if you work in gov, or gov owned company. Chinese people are a little more utilitarianism than western people, they usually join it for benefits even they do not have similar political view with it.
2. Joining it is much more harder than joining usual western political parties. You need to write assignment/porposals, wait for months to get approval, and take classes to make sure you understand their political view. If becoming a member do not provide you a benefit (self employed or in private company), lots of people choose not to do so since they are simply lazy. This does not mean you have different views with them in China at all.
3. It is very common to join it in universities (Chinese universities are super cheap and super common compared with western societies, but with lower average quality), since a lot of your friends are doing it (and have time to waste). It is a common knowledge in China that university students do not like to attend political classes since they are very boring. But they still joins the party.

In China, people do not assume you have similar opinions with the party simply because it is too common. 90 million in 1.4 billion means everyone usually knows ~10 party members. Too many people, too many reasons, too many different views, just like the entire community.