I agree with most of what you are saying but I think you (and not gonna lie, probably many other maxis too) dont understand why the confidence may be warranted.
I do not disagree in the least that humans are irrational and the markets will always reflect this. This is what creates volatility.
In the markets there are always general trends. And as you increase the time scale, that in turn smooths out the volatility. As your time scale approaches ∞ you are eventually left with a clearly defined trend line.
Most bitcoiners measure the success of bitcoin on a generational time scale. So what you may see as overconfidence, is simply the ability for a short enough time preference strategy to minimize the risk to a point where the outcome is certain enough that it warrants an all-in bet based on historical trends and fundamental analysis on the legacy financial markets, the state of worldwide economics, global politics, privacy, technological trends, and math.