These evil beings draw energy and power through these mass human sacrifices and occultic rituals.
Sometimes it's this. Sometimes it's war. Sometimes it's mass abortion. Other times it's 9/11.
Though I wonder. They used to have some level of cover and disguise. It seems that the mask has been slipping more and more.
This leads me to wonder whether or not the evil side has been systematically weakened, hence why they need to put on big overt public ritual displays.
They gain nothing by hiding in the shadows anymore, their only chance of success is by being overt and gathering as many dark followers as they can.
They need these rituals to maintain deception and power. And they need us to need them.
They are blood vampires and energy vampires.
It was a summoning..."call to arms"...demons and the vulnerable who are easily captured by them....it's like a recruitment mission. And their payment is blood sacrifice, as op said. Look closely, if you catch one of these rituals in the act, there will always be a recruitment process( i.e. concert/ show/ something that captivates massive numbers of ppl/ beings) and a payment process ( sacrifice of blood/ soul). Kinda like going to see a bar band and paying the $5 door charge.