To ensure that the domain names on the existing computer webpages are updated upon rescanning, you should enable rename detection under Configuration\Server Options. If rename detection is not enabled, new assets will be generated for the computers under the new domain.
You also need to ensure that the new domain is correctly submitted for scanning. A scanning credential with administrative privileges on your computers and read-only access to AD should be submitted and mapped under Configuration\Scanning Credentials. The new domain should be submitted for one or more scanning methods under Configuration\Scanning Methods as well. More info on submitting Windows computers for scanning can be found in
this knowledge base article.