The Enron scandal was one of the major financial failures around the year $2000.$ Describe briefly ALL of the following.

$(1)$ what caused it$.$

$(2)$ who were involved in and how they contributed to its occurrence.

$(3)$ what enabled its fraudsters to commit the fraud.

$(4)$ how it affected the people of interest such as the employees, shareholders, creditors, government, etc.

$(5)$ how it affected the regulations.