I figure it went something like this. A500 is out, someone from a cracking group reads a slaine comic or a thorgal comic or looks at boris paintings and says 'I bet people don't believe something like this can be made on the Amiga' so he sits down and does it. Everybody is amazed at their latest cracktro, and other group artists start doing copies, trying to outdo eachother on the technical merit only. not saying I'm glad people copied, but I AM glad they they pushed the limit of pixelpushing (heh) to where it is today. It's our job then, to use the knowledge and knowhow of theirs, but put it to more creative use.
And let's not forget that once again, not all demoscene artwork were copies. If you're a fan of frazetta (and frazetta clones) and boris, maybe C.Achilleos and a few others, you can spot MOST copies in the demoscene... the rest is NC. The logos which are some of the most amazing work, are usually original. Start there.