what they do to protect themselves?

Are you asking about preventing you're online presence being hacked?

or about keeping your game from being cracked?

The first one, right?

The first is a cyber-security issue. the second is about DRM technology.

For me, the normal precautions for cyber-security have always been adequate.

I didn't have to worry about DRM until I made a game popular enough to warrant cracking. IE: it was well known enough that cracking it would bring bragging rights to the cracker, which is why crackers crack games in the first place - solely for bragging rights - they just happen to injure gamedevs in the process.

What you are trying to do is predict possible risks and asking for ways to mitigate those risks.

Here's what you need to do:

1) Write out every risk you can think of to you, your game project, your company, etc.

2) To the best of your ability, rate each risk on the likelihood of its occurrence.

3) Then, assume that each risk will happen, try to assess the impact it would have on your operations.

4) Finally, sort each risk based on the likelihood of its occurrence and the level of impact it would have on your operations.
You'll have a risk matrix which has a list of things which are high frequency, high impact, all the way down to low frequency, low impact.

You want to spend most of your efforts on the high frequency, high impact items and you want to start taking steps to mitigate those risks. You can either work to reduce the chances that the risk would happen, or work to reduce the impact it would have on your ops (or both). You won't always have a 100% fail safe solution to everything, but you can work to get something to an acceptable level.

Let's take data loss as an example of a risk you might face:
The chances of data loss are medium. A hard drive could crash. A hacker could delete files. A virus might wreck your data. Human error. etc. etc. Lots of possible sources, all somewhat low, but combined, you get a medium level threat on its likelihood. The impact would be catastrophic, so medium multiplied by catastrophic should spurn anyone into taking preventive measures / action.
So, the best you can do is reduce the impact of such an event. To mitigate this risk, you should have a backup process in place! The frequency of your backups should be based upon how much work you can afford to lose. Every minute past your last backup is data living on borrowed time, so you're only as good as your last backup. Some business systems can't tolerate more than a few seconds of lost data (think of financial systems), others can't handle more than an hour of lost data, others a day, some a week, two weeks, etc. The shorter your tolerance window, the more expensive your risk mitigation solution is going to be.

Take a good bit of time to read through this:
https://en.wikipedia.org/wiki/Risk_management

I agree that you should seek medical assistance, even if you are not mentally ill or anything. Your paranoia might be "normal" but the way you handle it (always considering the extreme bad examples; possibly having the delusion that you have serious crimes "skeletons in your closet" in your past; stating that you were a stereotypical teenager yet thinking you were special enough for anyone to care) and let it take over your life is not.

I’m also anxious about what would happen if people were to make up and spread rumours or gossip about me. Remember Phil Fish, that guy who developed Fez? When I read about how he got hacked, it scared the daylights out of me. He literally had his life destroyed in one blow. People said he had a bad reputation and was very rude towards fans. So now I’m really worried about offending consumers too.

There are thousands, if not millions of popular people (rock starts, actors, developers, company leaders, whatever) who are not being hacked and are way more interesting than a game dev. You could be more afraid if you are a politician.

And maybe you should get a communications team or at least a secretary who handles fan emails.