[Amish with an attitude]

"I'm curious--assuming that this is a charter flight, with few passengers in a craft often used for charters..."

Likely a repositioning flight were they had a minimum crew showing up to pick up passengers for the money leg of the flight.

[Phinanceguy]

Those G-4's and 5's usually only crry a crew of 3. Pilot, co-pilot and flight attendant. They are configured to carry 12 passengers usually.