2 did flow naturally from 1. I honestly don’t think there’s much in TROS of JJ’s ideas for 2 and 3. I think he got caught up in off-base fan complaints of both TFA and TLJ and he tried to rethink the whole trilogy in one film.
If you read the Artbook for Force Awakens, many ideas from it were used in ROS. For example, Rey sabering an imperial ship, returning to Palpatine’s throne room, the Death Star wreckage underwater, DIO as a variant of BB8’s design, etc.
Samples:
https://i.imgur.com/ioTT9gl.jpg
https://i.imgur.com/0oPFoji.jpg
https://i.imgur.com/D25CcHS.jpg
I am plenty aware of the TFA art book. But those aren’t “JJ’s ideas for 2 and 3.” They are concepts floated for TFA. Hence my comment, “he tried to rethink the whole trilogy in one film.”