I'll be honest, I side with the park on this case. They reserved 8 sites and someone got there before you and picked those sites. As someone who travels in a group quite often, I appreciate a campground that will accommodate and allow us to get sites together. The purpose of camping as a group is to spend time together, eat together, sit by the fire together, etc. It doesn't work as well when 2 families are on the other side of the campground.
This weekend we are camping in a group of 5 or 6 families. Most of us can get there earlier in the day, buy my one good friend can't leave until 3pm or so, when his wife gets off work. Thankfully we have reserved sites (preferred method with a large group), so his site will be waiting for him when he gets there. Without reservations or the ability to have someone else "claim" a site, he would be at the mercy of luck.
Would you have been equally as upset if the sites were reserved and that group made reservations before you and got the good spots, but those 2 spots were still vacant the next day? The premise is still the same... they paid for the site and didn't occupy it.
I get that you are upset about it and that you struggled to find a site big enough for your large rig in a state park... but isn't that an inherent drawback to a large rig? We intentionally keep our trailer on the smaller side so we can go to more places. Our first camper was a 22' non slide. We could literally fit on any site... even a tent site if everything else was occupied.
