My account was hacked, which led to my apex being banned.

Heya,

Account issues such as bans cannot be assisted with here on the forums, only EA Support will be able to help you out with this issue.
You can dispute bans up to 3 times, any more will be ignored as far I'm aware.

If you haven't already, I'd highly recommend to properly re-secure your account with the help of this information.

More information on how to do so can be found in this EA Help article: EA Help - What to do if your EA Account has been hacked 

If one of your platform accounts has been compromised then you would need to follow the steps mentioned on the sites of these platforms.

Here are some guides from these platforms that might be of help: 

• [Steam] Recovering a Stolen or Hijacked Steam Account
• [Microsoft, Xbox] Secure your account if you think you’ve been hacked
• [Playstation] Phished (compromised) accounts and unauthorized charges
• [Nintendo] Nintendo Account Recovery Process 

Check if your login credentials have been breached

It's not uncommon for sites to have their databases breached, any site from Facebook up to a small blog site can have all the data on their servers leaked.
If you re-use your password between platforms (Which you shouldn't) then it's quite likely that your login information is already out on the internet for anyone to use.

Though worry not, you can check whether or not your login information has been leaked in one of these breaches.
This site: https://haveibeenpwned.com  Allows you to check both your mail and password to see whether or not they are in any breaches, if it's the case then it will let you know.

(Keep in mind that this site does not have data from every breach, so this site will not be 100% accurate, be sure to practice proper account security!)

Additional tips and information related to account security can be found in the Monthly AHQ Online Security Newsletter, which you can find posted periodically in this subforum:  EA Forums Info Hub | EA Forums 

From what I understand, EA does still action users that had TOS-Breaching activity on their account, even if they were hacked.
In some cases people fake being hacked, to try and convince EA Support it wasn't them, practically trying to see if they can cheat without consequences. (These kind of players lower the trust factor sadly enough, which leaves more players to suffer because of it)

It's expected of all users to practice proper account security, if they don't, then these kind of cases become quite frequent.
It's entirely possible they decide to uphold a ban to stimulate players to take care of their account, as it's not something that should be taken lightly.
(Do keep in mind that this is purely speculation on my part, though I believe that would be a reason to uphold a ban despite being hacked)

Overall the situation just sucks, but there isn't really anything that can be done on here. If you've passed the limit of 3 ban disputes, then that's likely all you can do, I don't think anything would be able to change the outcome sadly enough.