In addition to just wanting to raise the stakes for Dany, Grey Worm, and Tyrion, I’d thought there were also likely budgetary concerns behind the abruptness of Casterly Rock and Highgarden. There’s a note in the AmazonPrime edition of the episode about Euron’s parade being a last minute re-write that used hundreds of extras and took up a week of filming and a large portion of their budget. It wouldn’t be the first time that production broke down a bit with this series because they wanted to do something impressive with extras/real sets/horses and caused them to skip out on the action scenes
It’s sad that that note doesn’t surprise me in the least.