Can Central Banks and Policy Makers Prevent Bubbles?

If he had bought at the peak when Bitcoin was worth about $20,000, he would have lost by now 80% of his capital. So if we can see bubbles coming, should central banks and policy makers do something about them preemptively? I think it's actually a very interesting discussion point which makes sense to talk about now. A priori can bubbles exist? That depends on how you're going to define a bubble.