What wallet was that? You probably used a phishing link or downloaded some suspicious software. Hacking a wallet isn't easy and a hacker needs some help from you to be able to pinpoint your machine. It's like looking for a specific grain of sand on a beach. Be careful your PC may still be exposed (it most likely is) and if you transfer more money to your wallets it can be stolen again.
This is most likely the reason he got hacked. It's difficult to hack most wallets, for you to be successfully hacked, you would have given the hacker the tools he needed to achieve his nefarious activity. And it doesn't matter whether the hacker is poor or rich, fact is, if he had more than that, he would have probably wiped him empty and he ends up loosing a lot. People just need to be more circumspect with their activities online as hackers are always on the prowl looking for some loopholes you've created.