Why does the precious blood of Christ have the power to make disasters pass over?

Because it contains his extreme love and sacrifice. 

The prophet Isaiah prophesied the appearance of Jesus who would come 700 years later as follows

Isa 53/1~12 [… He grew up before him like a tender shoot, and like a root out of dry ground. He had no beauty or majesty to attract us to him, nothing in his appearance that we should desire him.

He was despised and rejected by men, a man of sorrows and familiar with suffering. Like one from whom men hide their faces he was despised, and we esteemed him not. Surely he took up our infirmities and carried our sorrows, yet we considered him stricken by god, smitten by him, and afflicted. But he was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was upon him, and by his wounds we are healed. We all, like sheep, have gone astray, each of us has turned to his own way and the lord has laid on him the iniquity of us all.]

We ourselves sinned, but Christ himself bore the penalty for our sins. Bearing our sins, he was pierced and his body was torn with thorns;

He willingly laid down his life for us on the cross. 

In this he demonstrated his own self-sacrificial love for us. 

He shed his precious blood for proof that he loved us. So, the destroying angel and even the devil our wicked enemy who know such a story very well, dare not touch us.

In the blood of the Passover covenant is included the love of Christ who has given us life by suffering the extreme pain of his flesh being torn and his blood being shed. All things are subjected to the blood of his sublime sacrifice, to his sacred love.

With such sacrificial blood we are sealed. By the power of the blood, all disasters pass over us.

Ps 91/7~11 [ A thousand may fall at your side, ten thousand at your right hand, but it will not come near you. You will only observe with your eyes and see the punishment of the wicked. If you make the most high your dwelling- even the Lord, who is my refuge- then no harm will befall you, no disaster will come near your tent. For he will command his angels concerning you to guard you in all your ways;. ]

The blood of the Passover lamb in the Old Testament was put on the door frames and lintels of their houses. In the New Testament, however, the blood of the Passover lamb is marked on our foreheads and hearts through the new covenant.

So even if the destroying angel comes near us, when he sees the blood of Christ in us, he passes over us. A thousand may fall at our side, ten thousand at our right hand, no disaster comes near us who are sealed by the precious blood of the Lamb in the truth of the Passover, the new covenant. That’s why we can be saved from disasters through the Passover

ChristAhnsahnghong established the Passover to destroy the devil and give his children eternal life.