This is a fundamental misunderstanding of the structure of the linux kernel, the nature of kernels in general, and the ways one performs automated verification of computer code.
Automated verification (including as done by rust in it's compiler) does not involve anything popularly known as AI, and automated verification as it exists today is more complete for rust than for any other system (because no other widely used language today places the information needed for verification into the language itself, which results rust code being widely analyzable for safety).
Human validation is insufficient and error prone, which is why automated verification of code is something developers have been seeking and working on for a long time (before rust, even).
Having "explicit" (manual?) memory management is not a benefit to enabling verification either by humans or by machines. Neither is using a low level language which does not specify enough detail in the type system to perform verification.
Kernel modules aren't that special. One can put a _lot_ of code in them, that can do effectively anything (other than early boot bits, because they aren't loaded yet). Kernel modules exist for distribution reasons, and do not define any strict boundary.
If we're talking about out-of-tree kernel modules, those are not something the tend to exist for a long time. The only real examples today of long lived out-of-tree modules are zfs (filesystem) and nvidia (gpu driver). These only exist out-of-tree because of licensing and secrecy. This is because getting code in-tree generally helps keep code up to date with less effort from everyone involved: the people already making in-tree changes can see how certain APIs are being used and if those in-tree folks are more familiar with the API they can/may improve the now-merged code. And the formerly out-of-tree folks don't have to run their own release process, don't have to deal with constant compatibility issues as kernel APIs change, etc.