Supply of the components to build EUV lithography machines and 30+ years of R&D. China is the greatest investor in reverse engineering and copy-pasta, but that only gets them so far…
Yeah and even just building the EUV source is really hard. You need to drip liquid tin, vaporize it into plasma with a high power laser, and filter the UV light that comes off of that plasma. Then to bring that EUV light to the mask you need to use very high quality Bragg reflectors, and you can’t use lenses at all because glass absorbs the EUV, so you need very well designed reflectors, and you need a high quality mask that needs to be kept in focus. All of this is done in a very strong vacuum, and you need to be able to add deadly gasses at well controlled temperatures. For all of this you need the latest and greatest simulation software, billions of dollars to spend, experienced engineers, and a decade of R&D. If you got the blueprints for every system through espionage, you still need billions of dollars, super specialized part (so you need to build multiple other factories for these parts), world class engineers, and years of design, alignment, and testing. By then TSMC has moved onto the next node because they have decades of experience and $134 billion in assets.