Safe mode?

I’m running 8.0.1 on a mac 10.5 (32 gigs of ram) tons of 3rd party plug ins include slate digital stuff…and for whatever reason after a crash my project wouldn’t load. it was hanging on ‘loading mix console loading channel: stereo out’. on every project i tried to open, in cubase 8 and 7.5 old, newish and new. hmm…
so i trashed prefs… same thing… i performed a clean uninstall/reinstall… same thing. safe mode… nothing (not in that order). i then opened an empty project fine. but when i tried to activate a project… same thing. i tried to disable various plugins from the plugins manager inside cubase, and still same thing.
i then shut down, unplugged a monitor (i have 3) and called it a day. this morning, started in safe mode again… and eureka! things working fine!
now, i’m freaked out to shut down or activate/reactivate projects… and was wondering about safe mode. is it only safe for that one time one starts in safe mode, or do i have to continue starting in safe mode until i can get some tech help?
what exactly does safe mode do? i thought trashing prefs was enough and i’m wondering why trashing the prefs didn’t work and safe mode did?
thanks in advance for any thoughts/advice!