The quote is “markets will tumble” by which he clarifies that it will be a temporary market overreaction not “crash the economy” like it’s 1929. Those are qualitatively different things.
He intends to make the market crash (or at least is taking actions that will almost certainly crash it), but he thinks it will recover afterwards. The first part is pretty certain with what they're doing. The second part is almost impossible to predict, because no one can really say what the break points are (i.e. how much it can crash and still quickly recover afterwards). See the mortgage crisis of 2008 for what an unexpected runaway effect looks like.
The quote is “markets will tumble” by which he clarifies that it will be a temporary market overreaction not “crash the economy” like it’s 1929. Those are qualitatively different things.