PUP.Optional.BundleInstaller is a generic detection that is used for bundle installers, aka bundlers.
Common infection method
Bundlers are typically installed by the users themselves, usually because they want to install the main program the bundler has to offer. Often unaware of the extra software that will be offered or even installed without giving the user a choice.
In most cases the built-in uninstallers and uninstall guides are far from complete. It usually takes a full threat scan with Malwarebytes Anti-Malware to remove all the PUPs and adware that might have been installed. As an example, a full removal guide for the OneKit SoftwareUpdater can be found on our forums.