Kolkata is an old city. And it is the home to every mainland religion and culture found all over the world.

Many of these people are not from around here. They can either be immigrants or officially declared citizens of India. I'm not going to argue about who's legit and who's not.

Regarding the simplified Chinese text on the video. Trinamool Congress had used slogans in Chinese before also, to familiarise the community with her party; wooing them for vote, in other words, as usual. No one screamed anti-India because it was an act of inclusion.

Here are some news articles for reading. They will suggest answers to some difficult questions are just a Google search away.

https://www.hindustantimes.com/lok-sabha-elections/lok-sabha-election-2019-in-a-first-mamata-banerjee-s-trinamool-campaigns-in-chinese-in-kolkata/story-TtKw1eXahUWa0jqZftoEMI.html. .

https://indianexpress.com/elections/chinese-community-kolkata-lok-sabha-elections-mamata-banerjee-5729495/

https://timesofindia.indiatimes.com/city/kolkata/chinese-community-leaves-a-mark-on-great-indian-elections/articleshow/69403549.cms