This is consistent with the screwed up Supreme Court decisions today. Of course they copied it. It’s virtually identical. Unreal.
While led Zeppelin certainly “borrowed” more than a few songs, this is not one of them. The spirit song has not melody. Only the first 2 chords are played exactly the same. Many songs revolve around a single chord with a descending bass line, both in minor and major keys. This case was a loser from the start. You can only copywrite melody and lyric. Pop and rock is basically the same 20 odd chords, with various different melodies and lyrics to those same chords.
Obviously you are not a musician. There is not a single melody written in the last 50 years that wasn't written before by someone else. The opening lead to Stairway to Heaven is a common Baroque theme so it has been around literally for hundreds of years. Just about every blues song and every country song and most rock and roll songs are all built on the same simple chord progression that dates back hundreds of years in folk music and tavern songs. The Beatles ripped off tons of these progressions from the ragtime era, early Jazz, and swing era.
Nobody has a copyright on chord progressions. It is almost impossible to write a song today that can't be traced to a song that was written before.
Frankly I am shocked that this case ever went to trial. It should have been tossed out in pre-trial motions. I hope the loser pays through the nose for costs. This kind of nonsense has no place in the courts.