If I steal $100000 from you, and you decide you value your relationship with me more than you value that $100000? Yep, you can just decide to let me have it and let it slide.
Believe it or not, deciding that you weren't wronged and not suing isn't a crime. It happens all the time. What people do with each other is up to them.
Did Bob allow his friend Jack to borrow his truck? No. Does Bob want to sue Jack for taking his truck anyway, and driving it into a ditch? No. Does Jack owe Bob big time for the mess he caused? Yes, but not in any formal legally binding way.
This works for corporations too. When two corporations find themselves at odds, threat of legal action is often used by one company against another as a leverage to resolve things behind closed doors instead. In a more amicable fashion - with no legal expenses of a protracted court battle and no loss of reputation on either side.
A lawsuit is not the same as a criminal prosecution. One is supposed to remedy damages, the other is supposed to be because it is in the public interest that people follow laws and we don't devolve into anarchy (or more dangerously, some might-makes-right society where it is more beneficial to appease the powerful than it is to pursue what is just).
It is possible for a prosecutor to decide it is not in the public interest to persue a prosecution (or that there isn't sufficient evidence to prove a criminal action beyond reasonable doubt), and certainly the victim's opinion could be considered, but ultimately whether criminal charges should be pursued is and ought to be based on a different test to civil matters, one focused on the public interest rather than mere restoration.