Can't install Microsoft SQL Server 2016 Release Candidate 3 (RC3) on Windows Server 2008 R2
I found the answer here:
Warning Setup Limited to Reporting Services for SharePoint by Alberto Morillo
Which, in short, says:

The only SQL Server 2016 features allowed to install on Windows Server 2008 R2 are Reporting Services (SharePoint) and Reporting Services Add-in for SharePoint products as mentioned on the &quot;Hardware and Software Requirements for Installing SQL Server 2016&quot; article created for SQL Server 2016 Preview (CTP versions).
You won't be able to install the Database Engine or any other feature because they are not supported on Windows Server 2008 R2.