Shigaraki was always destined to die because he never even existed.
Tomura Shigaraki is an artificial character, a name and a concept that was thought of and brought to life by AFO.
There is no 'Tomura Shigaraki' and there is no 'Tenko Shimura' because both of them were nothing but a face and a name AFO used and made his. He created them, forged them and raised them.
Tomura Shigaraki is the concept that Tenko Shimura was always destined to become. His mere existence only happened because of AFO's manipulation.
He was always going to die, be it as a sacrifice or in battle. The only thing he ever got to choose, the only thing in his entire life he had control over, was dying doing what he loved and staying loyal to his friends.
Tomura Shigaraki never existed and neither did Tenko Shimura.