Question

The third estate included approximately 98% of the French population under the old regime which group was exclusively part of the estate

Answer 1

Impoverished nobility refers to the nobles who had lost their wealth and status in a society. The third estate was created for commoners, and since wealth and status goes hand in hand, the 'nobles' who had lost their wealth is demoted and treated as commoners, which is why they're being put in the third estates.