No fraud there eh?
There were several shareholders' actions against the corporate officers responsible for inflating IPOs, against financial advisors for touting some over inflated issues and changes in the law (eg: Sarbanes-Oxley Act). The dive shown in your graph was induced by hype, betting on dot coms to do miraculous things (like the tulip hype in the Europe of 17th Century)--but, ony a few were unlawful. It was an emotional wave financed by debt and fueled by public irrational greed and wishful anticipation.