I wonder how can I check which unit activates another with status indirect?

I run Arch with Gnome and a Debian server. On my Debian machine I can see that output for systemctl list-unit-files --type=target --state=enabled shows, as expected:

default.target enabled multi-user.target enabled 

But on Arch desktop, surprisingly for me, it doesn't, although both: multi-user.target and graphical.target (my default on arch) are active. When I check the status of these units files they are both: indirect. When I list-dependencies for graphical.target it shows gdm.service and multi-user.target. In gdm unit file I do not see Also= in [Install] section. So what exactly activates graphical.target?

What is the reason of this "indirect" solution?