He's a public figure/celebrity ever since Bitcoin blew up. Take any celebrity and you can easily fill out this list.
Because he's famous, you're more likely to pick on him.
A journalist has the ability to take that to a whole new level by really shining a spotlight on it.
Just because it's easy doesn't make it right.
In fact you can do this with just about anybody. How and why is he at more risk than any other multimillionaire for whom all this information is public?
He would be in much more danger if he neither used his money nor kept his money in institutions that would raise alarms to authorities if you tried to force him to withdraw all of it.
This situation isn't really comparable to the general public learning that somebody may or may not have a few million in investments and savings accounts. It is closer to the general public (excluding the police) learning that somebody may or may not have a few kilos of coke stashed somewhere in their home.
This hypothetical bitcoin wealth, and the hypothetical coke wealth differs from hypothetical 'traditional' wealth in that they can be burglarized or extracted via torture without attracting outside attention.
But only if Nakamoto were actually able to spend it! If he's not able to spend it then he can't hire security I guess, but that would also put him at much lower risk of being burglarized for goods he can't give up. The important thing would seem to be making it clear he doesn't have access (that is, if he doesn't).
Stealing the fortunes of conventional multi-millionaires however necessarily involves interacting with the outside world at the time of the theft. Unless they are drug dealers anyway... there is a reason that drug dealers get hit by thieves so often, and it isn't only because the thieves know they will hesitate to contact police.
If he can no longer access the coins (either because he intentionally destroyed the keys, or because he neglected backups), then proving that to be the case would be damn near impossible. In this hypothetical case, Satoshi may very well believe that he has a better chance of making it unclear that he is actually Satoshi.
When you develop software based on your own novel framework, wouldn't you need to do several test-runs, performance runs, sanity runs in the process? Do you keep all the intermediate debug data? I know I don't. In this case bitcoins would be part of the intermediate data.