Dragon death effect becomes way bigger

When i spawn in a bunch of enderdragons and then kill them using creepers with an explosionpower of 100 the dragon death effect becomes way bigger sometimes taking up the entire screen

1 spawn enderdragons

2 place repeating commandblock with this command:

/setblock ~ ~1 ~ spawner{SpawnCount:10,MaxNearbyEntities:5000,SpawnRange:500,Delay:20,MinSpawnDelay:20,MaxSpawnDelay:20,RequiredPlayerRange:5000,SpawnData:{id:"minecraft:creeper",powered:1,Attributes:[{Name:"generic.followRange",Base:500},{Name:"generic.knockbackResistance",Base:1f},{Name:"generic.movementSpeed",Base:0f}],ExplosionRadius:100,Fuse:20,ignited:1}}