Why was Song Xiaolu from Guizhou Province demoted?

Do you want to ask why Song Xiaolu, the former mayor of Anshun City, Guizhou Province, was demoted? According to relevant information, Song Xiaolu was demoted because he voluntarily resigned from his job as mayor of Anshun City and was appointed deputy director of the Guizhou Provincial Department of Culture and Tourism. Song Xiaolu, male, Gelao ethnic group, was born in November 1969 in Zheng'an, Guizhou Province. He started working in July 1987. Member of the Party Leadership Group and Deputy Director of the Guizhou Provincial Department of Culture and Tourism (retaining the director level).