Why do some components vanish from the catalog list if one component has been installed in Rancher?
You haven't specified anything concrete, so I can't give you a specific reason...  But catalog items can:


Be mutually exclusive (e.g. you can't use ipsec and vxlan at the same time)
Be deployed at most once in an environment
Require the environment be a specific orchestration type
Require a certain range of Rancher versions
etc