You can't not decrypt the FileVault-encrypted drive on a Windows PC by default. Although some paid or free software claims to be able to decrypt the drive, some need the FileVault recovery key. You can directly use the FileVault recovery key to decrypt the drive on another Mac.
FileVault is a full disk encryption method for startup drives on Mac. If you connect the hard drive of the dead MacBook to another Mac, it will prompt for the FileVault recovery key to unlock the drive, if you want to use the drive on a Windows PC, you should turn off FileVault in System Settings on the Mac.