Per the Basement Tapes transcript:
They expect to be famous, to have a cult of followers after they die. They have advice for whoever those kids might be.
“If you’re going to go f—— psycho and kill a bunch of people like us … do it right,” Klebold says.
They (the teenage E & D from back then) would believe they accomplished not only kickstarting a revolution but had others succeed with far more devastating results (than what they shoestring budget pioneered). The current mass shooters ‘did it right” and in their name. But they’d always be ‘the first’, the two that started the movement, no matter how superior the weapons or how much bigger the kill count. Future successors point back to them for residuals credit.
The Everlasting Contrast 