For the comparison, Facebook/WhatsApp would fully cooperate with the police, if an account is identified to be some sort of fraud/terrorism/drugs, they will communicate the known identity of the user with last known IP and any information they have (under warrant).
OVH cannot do that, they only rent physical servers, they have no information about the software or the user. If the police comes knocking, the only thing that can be done is to shutdown or seize the servers.
The police must have something against some users of guerilla mail (not a surprise given the nature of the service), they probably went against the servers because they couldn't get a reply or any action from guerilla mail. I checked and found no contact information and no ownership information on their website.