These were probably some of the last civilian autos produced in 1941. Car plants were converting to wartime production of everything but cars: jeeps, trucks, tanks, and even heavy bombers.

It's true, the boxcars equipped for hauling autos were limited capacity, and it was easy to damage the merchandise. Things were so bad that by the end of the 1950s, the railroads had largely lost the new car trade.

However, by the mid 1960's the railroads were getting that work back. Today, a single, long multi level auto carrier with vandal resistant covering can carry 12 to 20 new cars. The highway auto carrier you see is delivering new cars to the dealers or wholesale/distributors from a railroad facility. (That is, unless you live close to an assembly plant.)

A solid train of auto racks can carry 800 or more new vehicles; that's a lot of trucks off the road.

Looks like a load of '41 Plymouths. Whoever bought them would be probably holding onto them for a few years due to war production starting in '42. My wife's great uncle had a '42 Plymouth with no chrome trim. He still had it in his barn when he died about 5 years ago. Still had the last inspection tag on it from 1969.

We see here an assortment of 1941 Plymouths and Dodges. The two cars on the back end of the truck on the left are Plymouths, and the two sedans in the back, on the backs of trucks (one is a light-colored sedan, covered with a tarp) are Dodges.

While trucks got larger, so did rail cars for auto transport. First, open cars that could carry as many as 15 cars, and later, the enclosed cars we see today, that deter vandalism and theft of parts during transport.

https://en.wikipedia.org/wiki/Autorack

Cars that can been seen well enough despite all the canvas look to be 1941 Dodge Custom Town Sedans. If you look closely at the rear of the first light-colored car from the left, you'll see a harbinger of Chrysler Corp. things to come: fins!

1940 movie with Humphrey Bogart, George Raft, Ida Lupino and Ann Sheridan.

Looks fly-by-night, but it was the future. The railroads held most of this traffic at the time, but it was in specially-equipped boxcars that tended to hold just four autos. The truckers had the same capacity, but a faster transit time and the ability to deliver to the customer no matter where they were located.

Eventually the trucks got bigger.