Very tragic, and heavily related to flight rules and procedures it seems. Simply put, the conditions - specifically it being night - were not good enough for any instrument approach to the required runway, but did meet the criteria for VFR flight in general. This has everything to do with the hills on final to 27R at KSEE, where the crew intended to land. This is a rare situation I think, demonstrating how much the responsibility of terrain avoidance lies at all times with the pilot, when flying VFR.
An IFR flight is better protected from any dangers in the local situation. Instrument approaches are designed to land somewhere safely if you can't do it without the risk of hitting anything by just looking outside. This results in
lower minima in most cases, but not all... Now if an instrument approach is ruled out by the weather and/or daylight situation, one should think twice about trying it visually, even if that is legal. This is one of those cases where everything comes down to airmanship, I suppose. The crew may have had reasons to still try it, like being familiar with the field. Perhaps we will know eventually from the investigation.
All that said, footage of the crash shows the jet flying through some low cloud. That's not allowed under VFR so the plan had already failed at some point before they hit the ground, at which a go-around, IFR recovery and diversion to another field could likely still have saved them. What a tragedy.
For the record: by daytime, two IFR options would have been available for a Learjet, but with little margin.
Erik
Edit:
P.S.
Here is an impression of the situation, from GE. Viewpoint below any glide path of course, but you get the idea.