The scripts of the controls are not combined in a single request, when the web.config key Telerik.ScriptManager.TelerikCdn.CombinedResource has value Enabled:
Steps to reproduce
1. Ad the following configuration in the web config and open a page containing RadControl.
<appSettings>
<add key="Telerik.ScriptManager.TelerikCdn" value="Enabled"/>
<add key="Telerik.ScriptManager.TelerikCdn.CombinedResource" value="Enabled" />
</appSettings>
Result: The scripts are not combined.
Workaround:
Enable the script combining in the ScriptManager declaration:
<telerik:RadStyleSheetManager runat="server">
<CdnSettings CombinedResource="Enabled" TelerikCdn="Enabled" />
</telerik:RadStyleSheetManager>