Seems like you'd want to subpoena source code or gmail history or something like that. Not much interesting in an office these days.
The warrant will have detailed what it is they are looking for, French warrants (and legal system!) are quite a bit different than the US but in broad terms operate similarly. It suggests that an enforcement agency believes that there is evidence of a crime at the offices.
As a former IT/operations guy I'd guess they want on-prem servers with things like email and shared storage, stuff that would hold internal discussions about the thing they were interested in, but that is just my guess based on the article saying this is related to the earlier complaint that Grok was generating CSAM on demand.