There has been a lot of cyber crime in recent years, e.g. see the recent wave of ransomware attacks. These criminals are mostly amateurs that know some exploits and use them. The NSA is a huge organization that employs many professional experts. Spying is one of their main objectives so you can be pretty certain that they are pretty good at it. Computer systems contain a lot of vulnerabilities and you can be pretty certain that they know a lot of them.

The computers of most people are vulnerable even to normal cyber criminals, the NSA is a lot more powerful.