Hello, @andyjoghi.
It’s hard to tell why your account was suspended. However, this is not the right place to ask. Your question regards a case that is between yourself and Twitter only, and is not suitable as a reply for other users.
You should open up a new ticket and ask the same question. You can do that from here:
https://support.twitter.com/forms
(If you followed all those 900 people within a very short time frame, Twitter might have been automatically notified of too much activity from your account and narrowed it down as “spam”. A lot of malicious accounts use this method to get their unwanted spam across fast.)
Best of luck,
~ @Ayu
Translator | TTC