I think you're conflating the
value of the real estate property itself with the GDP from the "industry", which has to do with property changing hands or tenancy.
(Those charts also fail to show how much of that income is from residential transactions/management versus commercial ones.)
It just doesn't stand to reason that if people entirely stop paying other people to buy and sell each other houses (even if it does account for the vast majority of that 13% of the GDP) that the economy would collapse completely.
However, if housing values collapse due to questionable (or worse) lending practices, as happened in the US around 2008, could collapse the financial system and thereby the economy. It might even increase the GDP of the real estate category, especially as a percentage, at the expense of the finance category.
More importantly, though, I don't think there are any voters that buy the notion that they could, for example, do away with their real industry, such as mining or manufacturing, and replace it entirely with selling each other their houses. Because of that, whatever conservatism they may hold would remain from that real industry, regardless of what category the statisticians put their income in.