Why After transplanting the shrub is it normal for all the leaves to wilt and die?

That can happen if the weather is very hot. It is best to transplant a shrub when the temperature is mild, not hot or cold. I transplanted a Forsythia bush yesterday afternoon. It is now morning and it looks fine. Here is how I approached that: 1. Dug a large enough space where it was transplanted to which was a generous pail size, tilled the bottom soil free of stones, added some fertilizer, covered the fertilizer with peat moss, filled that area that remained - one fourth with water. 2. Dug up the Forsythia, caring to not damage the roots, that was trimmed back a few days ago to about a yard high and about two feet in diameter around, leaving the root ball with the soil it had around it, destoned, trimmed the very lengthy roots not too much, placed it into a pail filled one fourth with water. Filled another pail full with the soil, destoned, where it was growing at. 3. Arranged the bush at the new site adding all of the soil and water that was in that pail, carefully placing the roots, with the longer roots circled. Lifted the bush to the same ground level it was previously. Held it there with one hand and filled in with the soil with the other hand, leaving room for a few inches of peat moss at the top of the bush. Gently firmed the soil, not too firm or too loose. Added the last few inches of peat moss, some fertilizer, then covered the fertilizer with peat moss. Gently blended the soils at the edge of the space and tamped all that firmly enough with my feet, not too tightly, not too loosely. Gently watered, thoroughly with a full watering can. The plant was watered three times during this process and was not soaked with water, the drainage was good where it was transplanted to, there wasn't any "drowning," because of poor drainage.