is it normal for ferns to fall over after transplanting and breakage
I purchased ostrich ferns. They were adult ferns. After planting, they looked great. I watered them thoroughly and they are in shaded area. The next day, they were all laying on the ground, and there was a lot of breakage. I tied them up with stakes. Will they come back, and is this normal?
No, they may stop growing for awhile after planting, but they wouldn't fall over and break by themselves. It sounds like something was stomping around in them --- dogs? cats? deer? woodchucks?
If the stems are broken through, cut them off. If they're just bent, you can tie them up to a stake. Keep them watered, they should send up new leaves after they get their roots going.
Here's an article on growing these guys: https://www.gardeningknowhow.com/ornamental/foliage/ostrich-fern/growing-ostrich-ferns.htm