Good point and I'm glad you asked! I couldn't find anything on why it's 'le'. Except doing a deeper search just now has turned up the reason, and you're correct. To make it sound posh more marketable in the fierce world of pretty village tourism!
In the 2012 Olympics, we would have come 7th in the medal table!http://www.ryedale.co.uk/ryedale/villages/thorntonledale/index.html#:~:text=It%20is%20in%20fact%20one%20of%20the%20most,area%2C%20to%20distinguish%20the%20village%20from%20other%20Thorntons.