Essentially, the ISO 26262 certification mostly verifies that the compiler release process conforms to a certain standard. It does not create an ISO standard for rust, not does it aim to. At part of the certification process we had to write a spec for the rust language, but it is a descriptive spec of how certain aspects of the rust language behave for one specific release of the compiler.
The certification builds on this to ensure that tests catch deviations between spec and implementation, known problems are documented etc. So rust as a language is unaffected, as is the rust project. The spec is open source and might be useful to others, you can find it at https://spec.ferrocene.dev/
The target sectors for ISO 26262 and related industrial certification are clearly sectors that require such certification: automotive, medical, etc.
Ferrocene itself however, is not only the ISO certified downstream of the rust compiler, it also offers for example long term support and tracking of known issues which the rust project does not provide. This is also important for certain applications that do not strictly require certifications.
Disclosure: I'm one of the founders of Ferrous Systems, but I'm only involved in the Ferrocene project on a moderately high level, so forgive minor technical inaccuracies :)