You clearly haven't understood the illustration (even though it is fully explained in the text) this is a diagonal wipe describing a transition of time (perhaps a clockwipe would make it more obvious).
We see the Republic era ships replaced by ships from the same era as ANH (time has passed).
Now we can see the Death Star being built but it's not being built right after the end of the Clone Wars but about half a decade before ANH after the Empire is fully established and their starfleet has been upgraded to what we see in the OT.