If I switch focus to IntelliJ (or other derived products like PhpStorm), the window maximizes directly in background. I have to minimize other windows in front of it before I can use it. Other applications maximize directly to front on clicking their taskbar item.
I'm running Linux Mint 19.1 with Mate Desktop with "Metacity + Compositing" as window manager.
Edit: User shaax mentioned, it also happens in Fedora with Plasma Desktop.