They have no high rate domestic airliner assembly lines, and they lack the domestic supplier base and capacity for the number of airliners needed. And they don't have pure Russian airliners ready for high rate production. The MS-21 needs engines and many parts from not western sources before this can happen. A certain commercial production boost might be possible by redirecting military staff, research and production capacity if they can spare anything at all. Even just rebuilding old soviet designs does not work, as the infrastructure and supplier base was lost.
It will be train rides for most.