maybe that's not the only reason john mcafee to stop promoting ico because it's risking his reputation and not all the ico being promoted succeeds because some are failing or slow to develop.
Yeah this seems the most valid and logical reason here , because in past he promoted many icos and worked as advisor in many project , in docademic i think he hold big part of supply and project raised funds less than hardcap still it is x10 of ico price within few weeks after ico end . so many accusations were put on him . also a ICO named pink taxi got some allegation , that was also promoted by him .
well we can only speculate , only he knows the exact reason .