Facebook never disables an account for no reason and certainly not for the fun of it.
Some examples include:
• Using a fake name or not using your full real name.
• Creating two personal accounts.
• Impersonating someone
• Continuing behaviour that's not allowed on Facebook by violating the Community Standards
If you think your account was disabled by mistake, you can appeal Facebook's decision, in your appeal, you must prove that Facebook made a mistake. Saying that you are sorry, that you did not know, that you will not do it again will be useless.