While being locked up and deprived of freedoms. Death is preferable to life in prison.
It costs more because of expenses around ensuring you have the right person and giving them a chance to appeal. That’s not needed here.
The barbaric act of crimes against humanity? There is zero doubt as to his guilt and role in causing said deaths.
There is no benefit to attempting reform, there is no risk he isn’t the right offender, and there is no benefit to paying to keep him detained.
For some crimes, death is fine. As it was for Mussolini.
What exactly is Qatargate?