Note, that's my vision how starships evolved, ignoring STE and ST:FC
It's alt canon (where Star Trek Enterprise happened on XCV-330)
They started from big spinning space stations-like ships,
It was achiemevent of space agency of united nations,
then in type 2, they got a classic saucer, but they kept the spinning element
the type 3 is (approximation of) Enterprise we love and know
It's alt canon (where Star Trek Enterprise happened on XCV-330)

They started from big spinning space stations-like ships,
It was achiemevent of space agency of united nations,
then in type 2, they got a classic saucer, but they kept the spinning element
the type 3 is (approximation of) Enterprise we love and know