In general, a facebook account gets disabled if you violate some Terms & Conditions of Facebook.
Posting content that doesn't follow the Facebook Terms
Using a fake profile name
Continuing behavior that's not allowed on Facebook by violating their Community Standards!
Contacting other people for the purpose of harassment, advertising, promoting, or other conduct that's not allowed!
Actually, the "Disable" is of two types, TEMPORARY ACCOUNT DISABLE and PERMANENT ACCOUNT DISABLE. If you think your account was disabled by mistake, use this form to request a review.