Only the optics is an ... interesting way of phrasing it.
There was a great Economist article a while ago that talks about this. ASMLs moat isn't just the know-how to build the machines themselves. It's a network of suppliers all across Europe, specialized businesses doing one little part better than anyone else in the world.
This is the type of thing that Europe is still leading in, and it'll be incredibly hard to reproduce elsewhere.
You don't just need to figure out how to build an High-NA EUV machine. You need to figure out how to build or procure all of the parts that go into it. Many of these suppliers have exclusive contracts with ASML.
Here's the article, de-paywalled: https://archive.ph/jP1HX
Yeah. ASML doesn't make the mirrors, but they have exclusive sales rights, exactly as you say. And yes, positioning them, for example, both in the fixed sense (mounting the mirrors in the machine) and in the dynamic sense (rapidly positioning wafers to nanometer-or-better accuracy below the beam, I forgot how quick exactly but it's 10s to 100s of times per second to maintain production rates) is very much not easy either. But it's "been done" (by teams of phds). Producing the mirrors has not been duplicated.
Of course, producing the EUV beam in the first place has also not been duplicated and it's Californian technology.
Intel 18A has a different strategy all together. I mean, it's not like they're saying much about it, but from the little we know, it's very different.
No the beam source we know how to create; it's just that the way to do so requires a factory sized machine that better be feeding 10~30 steppers or a pair for uptime/maintenance windows and then probably more like 50 steppers.
Free electron lasers are not hard at "mere EUV", and the accelerators to feed aren't either, it's just that an efficient setup requires recycling the beam which means bending it back which means a large (factory hall sized) accelerator at the beam energies needed for good EUV light.
Uhh, you do not need an accelerator to generate EUV. It's literally just molten tin hit with a laser.
Weiss makes the mirrors.