CREATE TABLE table_24396 ("State  ( class ) " TEXT, "Vacator" TEXT, "Reason for change" TEXT, "Successor" TEXT, "Date of successors formal installation" TEXT)

What was the reason for change in staff in formal installations on March 15, 1865?
SELECT "Reason for change" FROM table_24396 WHERE "Date of successors formal installation" = 'March 15, 1865'
SELECT "Reason for change" FROM "table_24396" WHERE "Date of successors formal installation" = 'March 15, 1865'