Which highlights this:
'Users dug up an October 2020 tweet from Musk in which he posted that SpaceX wouldn’t build a flame diverter on the launchpad, but acknowledged that “it could turn out to be a mistake.”'
How much it would have cost to build a flame diverter?
[1]: https://www.thedailybeast.com/the-faa-grounds-starship-after...
I think they should have considered an above ground flame diverter - which would have been far cheaper. It would consist of a simple pyramid below the rocket.
However, this wasn't the case - the joints were vertical (as would be normal for laying a parking lot), and the end result was exhaust gasses went through the joints and lifted the slabs up, causing many of them to get blown away.
If they add both a trench and a deflector that gives them some degree of control of where the exhaust goes once it leaves the underside of the rocket, so you could lead it away from critical pad infrastructure and direct it out to some empty area to disperse. Obviously all that requires quite a bit of space, which they might not have available.
https://youtu.be/LNkmwrTjKuo (NASA) https://youtu.be/dU9TTRfM_9Q (Interesting Engineering) - at Kennedy Space center.
The system at Boca Chica is shown at https://youtu.be/OsbnYp0FYKU which looks like a garden sprinkler compared to what is at Kennedy.