Nearly every commentary I consulted, including those most lauded among biblical scholars, identifies Esther as a diaspora story,
composed by an unknown author in the 4th of 5th century BC.
The Bible is a «symposium» of works
by a number of persons,
composed of many writings, written over a period of hundreds of years, some only preserved in fragments,
by unknown authors, written on animal skins (for they had no paper as we know it), with no printing presses to preserve the writing... It's a marvel we have the Bible at all.