Hello, and welcome back to Just Answer.
I'm so sorry this happened to your blanket and also sorry to be the bearer of not such encouraging news, but there's probably not much you can do about the shrunken blanket. Washing it destroys the lanolin in the wool, that keeps it soft and keeps the fibers in their natural state, and the fact that it was put into the dryer, worsened the situation and increased the shrinkage.
You can try to 'block' (shape) and stretch it by first soaking it in lanolin (can be ordered online or possibly bought in knitting stores) to restore this important component, which might loosen the fibers which were seized up, as a result of the washing/drying process, and then try laying it flat and tying it to your bedposts (if you have four), for example, to stretch it. However, it's very possible that the fibers are too tightly enmeshed to stretch it much.
I suggest bringing it to your dry cleaners and asking if they might be able to stretch it. If not, perhaps you can cut it into smaller pieces, apply some non-fray solution to the edges (sold at sewing and craft stores) and add borders (iron-on, sew-on, fabric glue-on) of your choosing, to make scarves, hats, perhaps a skirt(?) if possible.
Another idea, if it is not able to be stretched back to it's original size, is to give it as a gift to someone as a baby blanket; however, keep in mind that mohair is an 'allergic' material to some people.
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