Predict a crash continuously and one will arrive, and the years of being wrong in between vanish from the retelling. Permabear content performs well because fear is engaging and because caution sounds sophisticated.
As with permabull, the problem is invariance rather than pessimism. A bear case with conditions, levels, and a statement of what would refute it is analysis. One that is restated identically for a decade is a brand. See cherry-picking.
Related: permabull, cherry-picking, belief-perseverance, narrative-fallacy