19th century World's Fairs created to hide real ancient high-tech buildings in the US and Europe?

It was already tried to discuss 2 years ago here on GLP, but with the current global situation it's more interesting than ever now:

This documentary summarizes it well: For the 19th century and early 20th century World's Fairs in various locations of the United States of America and Europe, impressive and huge Roman-Greco style antique looking buildings were created which are difficult to explain in context of available resources of that time.

It's said that they were made of plaster, wood and fabric as the intend was to dismantle them at the end of each fair.

Though most of those huge buildings were afterwards said to have been rebuild in concrete and stone due to the request of the local population. But if you see under which limited resources those cities has to work with at those times, it's difficult to explain how they managed to do that.

Documentary:


List of still existing World's Fairs buildings:
[link to en.wikipedia.org (secure)]

I agree with many of the documentary's statements. For example pointing out specialty of this real antique style compared to some imitation buildings which were added for the fairs. The real style presents its special geometric proportions and fractal allegory which wasn't just pure decoration but had physical meaning. Just a simple example: The facade of early 20th century city houses created air turbulences which improved the temperature management of the building inside. It also was noise absorbent.

But I'm not agreeing with the documentary's slight tendency into communist ideas as they focus at times on proposing a global almost identical culture as source for those buildings. They also advertise JRR Tolkien and try to sell the Hobbit village as wishful future for large parts of the population. Sure, the village is nice for a weekend trip or holiday, but face it: Which of the long term villagers would consider traveling to another continent, developing some more efficient plough or consider going to other planets?