Why wasn't Saint-Exupéry able to cover more distance before his 1935 desert crash?
This site has more details on why it took so long to get to Libya
https://www.thisdayinaviation.com/30-december-1935-wind-sand-stars/

After taking off at Paris, Saint Exupéry followed the Seine to the valley of the Loire and continued south, crossing the southern coast of France near Marseilles. The fliers had been over the Mediterranean Sea for a short while when they saw fuel leaking from the left wing. Prévot calculated that they had lost 20 gallons (76 liters) of fuel. They turned back and landed at Marignane to repair the leak and refuel before continuing.  Saint Exupéry wrote, “I drank a cup of coffee while the time lost hurt like an open wound.”
Once again heading across the Mediterranean toward Tunis, they encountered low clouds and heavy rain which forced them down to just 60 feet (18 meters) over the water. They flew along the coast of Sardinia as the weather improved.
F-ANRY crossed the coast of Africa at Bizerte, Tunisia, and about fifteen minutes later landed to refuel. With two hours of daylight remaining, Saint Exupéry and Prévot took off again, now heading toward Benghazi, Libya. They landed there at 11:00 p.m., local time, and in just twenty minutes the airplane had been refueled and once more, they were airborne.
Flying east after moonset, Saint Exupéry and Prévot were in total darkness. After three hours a faint glow of his navigation lights on the airplane’s wingtips told Saint Exupéry that he had flown into clouds, with visibility measured in just feet.
At a time when there were no navigation aids, pilots had to navigate by their compass, airspeed indicator and clock. Though Saint Exupéry had met with meteorologists to plan his flight, there was no way to update the weather information after takeoff. He had no way of knowing whether an expected tailwind had held, or if it had changed; was his speed across the ground faster or slower than planned? Had the wind blown him right or left of course? Had the atmospheric pressure changed, causing his altimeter to read higher or lower than the airplane actually was? Flying across the emptiness of the  Sahara Desert with no landmarks, in total darkness and now just a few feet of visibility, he and Prévot could only guess at their position.
4 hours, 15 minutes after taking off from Benghazi, the C.630 crashed into gently rising terrain at 170 miles per hour (274 kilometers per hour).

More on the plane:

The Société des Avions Caudron C.630 Simoun was a four-place, single-engine, low-wing monoplane with fixed landing gear. It was built of wood, with the surface of the wings and fuselage covered in plywood sheet then covered with doped fabric. Carefully curved aluminum sheet metal covered the top and bottom of the fuselage. The C.630 was 8,70 meters (28 feet, 6½ inches) long with a wingspan of 10,40 meters (34 feet, 1½ inches) and height of 2,25 meters (7 feet, 4½ inches). The airplane’s gross weight was 1,230 kilograms (2,712 pounds).
The engine was an air-cooled, normally-aspirated 9.500 liter (579.736 cubic-inch-displacement) Renault Bengali 6Pri inverted inline six-cylinder overhead-valve (OHV) engine rated at 180 cheval vapeur (177.5 horsepower). The left-hand-tractor, direct-drive engine turned a two-bladed, metal Ratier variable-pitch propeller. The propeller could be set to coarse pitch by a mechanic prior to takeoff, then an air bladder mechanism could change it to fine pitch for cruise flight.
The C.630 had a maximum speed of 310 kilometers per hour (193 miles per hour). The service ceiling was 7,500 meters (24,606 feet) and normal range was 1,260 kilometers (783 miles). Twenty C.630s were built before production changed to the slightly improved C.631.

Not a lot different than my Cessna Cardinal, which is a little wider (35'6&quot;), 4 seats, fixed gear, and 180 HP Lycoming engine with constant speed (variable pitch) prop totally controlled from within the cockpit. Service ceiling only 14,600 feet (altitude where climb rate drops to under 100 ft/min). Gross weight 2,500 lbs. Max speed (never exceed speed) is 192 mph, with max cruising speed of 158mph (speed not to exceed except in smooth air). Cardinal carries less fuel most likely, just 50 gallons, my best range at 10,000 ft is 615 miles.  I think our longest flight has been about 4 hours, can only listen to ATC for so long!