C2Rust basically compiles C into a very low level program in Rust. You've then lost the C idioms. Now you have to decompile the low-level rust with pointer arithmetic into Rust abstractions. That's very hard, probably harder than converting C idioms to Rust idioms, checking to see if the result will be equivalent, and falling back to low-level compilation only when absolutely necessary.

The key to this is figuring out the comparable representation for data. Mostly this is a problem with arrays, since C's array/pointer system lacks size info. All C arrays have a size; it's just that the language doesn't know it. The trick is to figure out how the program is representing the size info. Somewhere, there was probably a "malloc" which set the size, and you may have to track backwards to find it. Then you can replace the C array with a Rust array that carries size information, and maybe eliminate variables which carry now-redundant size info.

That would produce readable Rust. But it requires whole-program analysis. That's OK, that's what gigabytes of RAM are for.