why did you do a full reset and lose data when you could have posted about your problem here and got help? http://wiki.meego.com/N950/Fixing_MALF_state the site is a good wiki for fixing the reboot loop or at least to retrieve data before reseting everything. You could have done a simple search and found this out too instead of posting your regrets here after everything has been done and dusted.
on your question of why did it happen did you use N9QTweak too? Maybe some tweak conflicted with home screen settings to cause the reboot loop. Without info on all the apps and tweaks in your system its difficult to pin-point the issue. Home screen settings works perfectly for many users here so it should not be solely responsible.