I've played in a lot of different games and from what I've seen Minecraft basically tops #1 of all games where users experience 'Hacks'. Why is this? Well I can give you one really good guess so let me explain:

You have a:

Minecraft account

Email Account

Minecraft-related websites accounts (How many? who knows)

Youtube Account

Youtube account is your google account, they rarely get hacked and since it being pretty much Google and that they have really good security to keep your account safe, you should be good.

Minecraft-related websites such as PlanetMinecraft and many more I just can't think of the top of my head are quite big in number, you probably signed up to quite a few and probably used the same password as your minecraft account so it's easy to remember.

Minecraft account, doesn't have the security features google or Facebook has, always seems to be the target for some reason (I don't know what is so special about mc accounts)

Email account, Is your backup to all the other accounts, if you lose any account on any website, you can pretty much regain access by resetting the password through a link in your email.

So what is going on here? Well I can tell you that data breeches are very common, the smaller sites will not go out their way to tell you that they've been breached because it will effect their reputation. So any usernames/emails/passwords which you use with those sites (usually same information) will be taken and used on other sites like Minecraft and even your email if you are silly enough to use the same password.

The Solution?

Use a unique password for each and every site (Or at least the important ones)

Change your passwords once a year

Type in your email address at https://haveibeenpwned.com/ and see any sites that are known to be breached, change the passwords for those sites.

If this seems like too much work for you to be secure, then I suggest you install LastPass Google Chrome Extension and Mobile Application. It's an app that pretty much focuses on making it really hard for anyone to hack your account and I would admit, I've never been hacked on any account for the past few years. 

So yeah, it dies down to simple security, don't use the same passwords for different website accounts. If anything keep Websites / Email Address / Username / Passwords  in a spreadsheet document safely stored on either Google Drive or on your pc. 

Be secure people!

Wabbit.