OP has said that they are in Michigan and had to drive two hours to get to airport where they could get Delta to Athens. That tells me they are in a small town in Michigan, probably not a lot of flight options. Once you miss that evening flight heading across the pond you are pretty much stuck going the next day. . It’s not like a domestic flight with a lot of options, though you probably don’t have a lot of options from a small airport anyway. Even if OP had booked themselves the same thing would have likely happened. When flying across the pond always better to book at least 2 days before the cruise, though 3 is better.