Vigilance vs Deathtouch?

I'm currently playing the event "You've Found an Entrance", and I came upon an unexpected combat situation in Node 1.
I'm using a variation of OmniHulk deck. The loop wasn't looping, so I passed the turn to Greg, and that's what the pre-combat situation looked like (only relevant Evergreens listed):

My side:
Atraxa, Grand Unifier (Flying, Vigilance);
Underrealm Lich (Prevent Damage);
Combustible Gearhulk.
Greg's side:
Lightfoot Rogue (Deathtouch).

When Lightfoot Rogue attacked, he also got Berserker from the D20 roll.

What I expected to happen:
Atraxa's toughness was higher than Lightfoot Rogue's power, so I expected her to take the attack from the Lightfoot Rogue due to Vigilance (that never took Deathtouch into account) and die.
What actually happened:
Atraxa's Vigilance didn't trigger, and Lightfoot Rogue couldn't attack her directly (because of her Flying), so he attacked Underrealm Lich, who survived the Deathtouch attack due to his Prevent Damage.

My question is why?
Hypotheses:
1. Vigilance only triggers against attacks targeting PW and doesn't protect other creatures. Meaning that should Atraxa be the only creature in that combat situation, she'd intercept the attack (Berserker or not), but she wasn't. I never noticed such behavior before, but I also never paid much attention to it;
2. Vigilance does protect other creatures as well, but Underrealm Lich, attacked by Lightfoot Rogue, had Prevent Damage and was in no danger, so Vigilance was not triggered;
3. Vigilance was upgraded to read "Deathtouch" and prevent sudden death (which is in line with the idea of protecting while staying alive) the same way Vigilance would always trigger if it's paired with Prevent Damage, no matter the toughness and power difference. Probably, I just missed the notice about that change?