Expectation: Customer wants to sync all the Events to Gainsight that are related to Contact.

“What we want to have is to Sync all those events that are related to Contacts. However, when I select the dropbox "Related To" I can't find the Contacts object there. It is not surprising that I can't find the Contacts object there, because "Related To" may be referring to the "WhatId" field. The majority of Events we have are related to Contacts and we can see a large list in the Salesforce timeline. “

But this integration basically works on the Related to Field, which is What Id in SFDC and doesn't constitute Contact object.
It is for this reason this Contact Object is not populating. And if the Related to field is empty, then it is not possible to sync those event in Gainsight (this is a current product constraint). 

So, Do we have any option on how to include those Events related to Contacts into the Gainsight Timeline