The horses didn't die, it was fine.
And if a bull is after your horse, if you get in the way it is only going to run you over too. There is nothing you can really do to help the horse than to distract it.
The person commenting on this video is absurd - you can clearly see the guy threw his hat to distract the bull, but the horse threw its head and hit it, clearly an accident.
The people that run & the adults who help with High School rodeo are all voluntary and work very hard to make this thing run for the kids. All the clowns and arena workers are parents who volunteer their time to make it happen for their kids and others. They are highly unappreciated and this video is 100% ridiculous.