Frankly I cannot see the logic of closing the terminal completely for up to 6 months in the hope that things may have improved by then. The cost of keeping it open for 4 days per week, as is now the situation, is manageable when balanced against the total loss of revenue from Ryanair and having to start operations from scratch some time in 2021 if the terminal was completely closed now. No doubt some of the employees that have been retained have been re-deployed from time to time to other of the airport's operational activities which continue to produce revenue.
To totally throw in the towel would hardly reinforce to current airline customers the stated attitude that SEN expects to be able to revive its fortunes as the industry itself recovers.