Steps to recreate:

1) Have a multi-monitor setup of minimum 2 monitors.

2) Open the Minecraft Launcher.

3) Maximize the window while on the primary monitor.

4) Close the Launcher.

When reopening the launcher, the launcher will open on the secondary monitor instead of the primary monitor it closed on. It is possible to fix this issue by restoring down the size of the window, moving it to the primary monitor, and closing it once again. To maintain expected behavior, the launcher must not be maximized at any point.