JOEL - According to some autobiographies, after Amasa Lyman returned from a mission to Europe in the early 1860s he moved his family to Fillmore. One of his wives, Eliza noticed:
"Bro. Lyman seemed to feel uncomfortable in his mind and I thought many times did not enjoy that portion of the spirit of the Lord that a man in his position should. I did not know what was wrong with him but I could see that he was very unhappy. He left his family mostly to their fate or to get along as best they could, although he was with them." (Autobiography and Diary, July 1863.) His condition would worsen until it would end in his apostasy and excommunication on 12 May 1870. Some of Amasa Lyman's beliefs may have contributed. At one time he was stressing radical perfectionism which actually denied the necessity of Christ's atonement.
A few other entries in journals tell of his quick temper and being easily offended on other occasions, which may all have contributed to his downfall.
Later on Amasa’s excommunication was reconsidered after his death, and his blessings, priesthood, and families were restored to him. I guess after considering how important his work was in the building up of the Church, the presidency decided that he deserved to be reinstated.
Restoration of Temple Blessings is an actual ordinance that allows endowed persons, who were excommunicated and later readmitted by baptism, to receive their temple blessings again. They are not endowed again, since these blessings are restored through the ordinance. This happens quite often for living individuals in the Church today who want to return. It does not happen very often for those who were excommunicated before they died, unless after their death they were later found to be innocent of wrong doing. First Presidency approval is required to perform this ordinance for the dead.