To be fair, they did get some pretty decent damage in on their surprise round. They just didn't get many more chances.
You comment does assume a bit of context. They might be a new DM just learning how to do stuff, in which case it's perfect fine to not be perfect every session.
Heck, it's perfectly fine to not be perfect even for experienced DMs. The most important thing is that whatever happens both the players and the DM learned something.