When you install a MS product like SharePoint, the OS will check the validity of the certificates that digitally sign the code by checking the CRL (certificate revocation list). If you don't have Internet connectivity, the install will complete but will
take somewhat longer as each CRL request times out (20-30 seconds each I think).
There is a setting in AutoSPInstallerInput.xml as follows:
<!-- Switch off checking whether the code-signing certificates used to sign the SharePoint code have been revoked. This slows down the
start up time for SharePoint, particularly if the server cannot connect to the Internet to perform the revocation check. -->
This might help in a case like yours where the server doesn't have Internet connectivity.