A quick correct pilot action would have prevented both accidents. The whole reason that MCAS, even in its previous certainly faulty version, was approved was the fact, that there is always the possibility for the pilot to stop a runaway stabilizer by using the cut-off switches. Which was done only just before the second crash, but to late and they were flying too fast, so they struggled to manually correct the trim. While the accidents were certainly caused by MCAS activating in error, there was at least a chance of preventing them.