When using the summon command to create a firework the fireworks does not register any internal data about explosions, I've tried multiple variations of formats for the command and none result in a firework that explodes like they did before 24w09a 

 

command used in 1.20.4: /summon minecraft:firework_rocket ~ ~0.1 ~ {Silent:1b,Motion:[0.0,0.0,0.0],ShotAtAngle:1,LifeTime:0,FireworksItem:{id:"firework_rocket",Count:1,tag:{Fireworks:{Flight:1,Explosions:[

{Type:1,Flicker:0,Trail:0,Colors:[I;65535]}

]}}}}

video attached

 

example command used in 24w12a: /summon minecraft:firework_rocket ~ ~0.1 ~ {Silent:1b,Motion:[0.0,0.0,0.0],ShotAtAngle:1,LifeTime:0,id:"firework_rocket",Count:1,tag:{fireworks:{explosions:[

{shape:'large_ball',colors:[16711680],has_trail:true}

],flight_duration:2}}}

24w12a failed results.mp4