All of the factors explained are actually relevant.
It doesn't matter how many event or tech tree vehicles were given to France, the tree would never be under any conditions more popular than nations such as the USA, USSR and Germany simply due to demographics, general historical interest and the playerbase populous.
The reason being of why more obscure and "strange" vehicles for the larger nations is because they have a demand and interest as well as the fact generally more information is available. In most cases, there are often examples in the Soviets case sitting in museums that have much more access.