Makes sense - hadn’t realised they were using pre-existing sets/equipment etc.I would imagine the cost of flying there and accommodating everyone in France was financially cheaper than doing everything from scratch in the US. Everything was all in place after the French version of the show had finished filming (I believe it tanked in the ratings anyway).
Tea on Reddit suggests that they paid the audience a small amount of Euros to stay for the purposes of filming.
Gutted we can’t watch it!