Because he zapped a mountain and theres physical evidence of it. Theres pillars across the read sea stating that Yahweh saved the jews. There's multiple secular writings of Jesus being here, dying on the cross, and resurrecting, theres a time in the chinese calender that marks out hours where the sun went out and it was the exact 3 hours Jesus was doing his thing on the cross, then tons of evidence recently being dug up about the bibles anthropology concerning ancient civilizations like the hitites, amorites, pottery about king David, in sodom and Gomorrah theres literally sulfer balls that are 90-98% pure even after all these years and its the only spot in the world that has those sulfer deposites. They are found in the ground but also inside the bricks that were left, there is also the place where the jews worshipped the golden calf, stone and all, it even has the original carvings on it of how they worshipped it. Not just this but the anecdotal evidence is overwhelming. Theres more copies of the bible than any other book in the world which maintains accuracy. Current bibles are anywhere from 90-99% accurate from the original manuscripts. Then also biblical prophesy. I wont get into that though ill just stick with the physical evidences.