Unless they are trying to appeal to Australian fan, my money on the real reason is that they wanted the glamour of a night race in Vegas.
This was a decision about some target group, I'm sure.
Some combination of “strip looks better at night”, “showtime or post”, “needs to be viewable by Europeans” and so on.
They’re just saying that because it sounds better than that the strip looks cooler at night.
They’ve timed the race to be when the strip looks coolest but after the casino traffic has peaked.
For me, I’m all on board with “‘The Strip’ is built for showing off after the Sun goes down” is a much better marketing point than “European fans may watch it from a café, if they are up early enough.”
But that’s just me, a minimally interested F1 watcher who spends time in Las Vegas.
I wonder how much input the city had. Maybe they decided it was better to try to recruit Europe than to win over America?