'twasn't the original plan. George Lucas just wanted to milk it for all it was worth. Episodes 4-6 are still the best ones though.
The studio would only give him the money for the last 3... at that time they thought star wars would flop. He made the first 3 in the late 90's early 00... at the request of the fan following.
Because they wanted to.
I don't even like star wars and Im aware that the "first" was made last...