I can only give you general guidance on the law because I am only licensed to practice in Oregon, and I only have limited information about the situation you describe. Nothing I say should be construed as legal advice, and I cannot represent you in this matter.
If a person signs another person's name without their permission, they have committed fraud. If they do it for personal gain, they have committed a felony in many states.
It is possible that a person could give another person blanket permission to sign their name without having prior knowledge of the specific instances in which the person would sign their name. Therefore, it is possible, based on your brief description, that the person who signed the other person's name had permission to do so.
Signing another person's name, even with permission, creates a risky situation for the person who does the signing. If they are later accused of fraud or another crime, they will need for the person who gave them permission to honestly confirm that they did so. If that person does not confirm that they gave permission, either because they do not want to be held responsible for signing the document, because they have died or disappeared, or because they disagree about having given permission, then the signer could be in very serious trouble.
It is very risky and unwise to sign another person's name, even with their permission. Misunderstandings can occur about the scope of permission. It also looks very unprofessional for both people if anyone else learns of the practice.