Every advanced ancient civilization had astronomical observatories and political leaders routinely relied upon personnel at these facilities for information about when to plant and harvest crops. If your livelihood depends on this sort of thing, there may be an incentive to invest in improving instruments and models.

The artifacts that we have found represent a small fraction of what these people produced and used. Are there going to be any iPhones (or Commodore 64’s)that will survive to thousands of years from now? If so, will future archaeologists be able to turn one on?

The modelling for the movement was simple: The Moon rotated on a cycle, whose center was itself rotating on a cycle centered at Earth (see [2] from [1],) but the part of the antikythera mechanism that was devised to simulate this was purely brilliant!

[1] https://physics.weber.edu/schroeder/ua/BeforeCopernicus.html

[2] https://physics.weber.edu/schroeder/ua/Epicycle.png

“With LEGO”, rather than “by LEGO”. A remarkable achievement nonetheless, but nothing compared to the original Greek mechanism – the independently acquired celestial knowledge, mathematical ability, and the technical skill required to complete it is mind boggling given the era.

He's trying to do at least one example of each type of required task with tools that would have been available at the time. Most of the gears were actually cut with a gear cutter (consisting of an electronic indexer on the headstock of a mini lathe and some Sherline lathe parts mounted on the mini lathe's cross slide, using a homemade 60° D-bit). That has included making (and using) a pump drill with various flywheels he's made from bronze he alloyed and cast himself, making drill bits and files from iron, which were then case-hardened (because steel, as such, wasn't a thing back then), along with various other plausible tools. The only place he hasn't gone is making a lathe, for which there is ample documentary evidence (by the standards of "ample" in documents from antiquity).