I think that the point is that after the explosive growth stage, if something is a bubble you end up in a (possibly) short period before the bust. While you can make money investing during the period, the risk is that much greater that you will miscalculate when the bust will happen and take heavy losses. So:

  1. Explosive growth is over, you can't make money anymore.
  2. That's not true, you *can* still make money.
  3. But attempting to make money at this stage is riskier.