In past shortages, that demand crash is precisely what happened. Considering how long a new fab takes to pay for itself, and how thin the margins are in fabbing trailing-edge chips that have been around for years, it would be a major risk to lay out more capex than your road map from 2019 suggested. Meanwhile, if you just keep doing what you're already doing, utilization is high and prices are rising so you're guaranteed to turn a rewarding profit. There's not a major private-sector incentive that would justify costs whose amortization would require consistent demand for several years.