The use of the name Super Bowl to describe the championship of pro football predates the official adoption of the name for what was originally the NFL AFL Championship Game. Of course that was before you were born:-)
For many years “win a free trip to the Super Bowl” promotions were everywhere both nationally and in local ads. These promos had no connection to the NFL. This whole “Big Game” nonsense came down the pike later. Maybe when you were a teenager. Once the Super Bowl hit huge is when the NFL started throwing their weight around.
The name was trademarked in 1969, and no the name doesn’t predate the merger, though it didn’t become official until the 3rd Super Bowl (which kind of funny).
They probably did have connection to the league, or the league just didn’t notice. It wasn’t as huge a deal then, it took until the late 70s for it to become an EVENT. Until the NFL was huge it didn’t have need to throw its weight around because there wasn’t as much reason for people to use their trademark.
There’s nothing new or unique about this, you must protect your trademark or you lose it as I showed in the previous post. And the more valuable it is the more you have to fight for it. And there are few trademarks in this world as valuable as the ones the NFL has.