When the Empress Wu took power in 690, the Tang Dynasty was relatively new. This was a dynasty whose reign is seen as a second Golden Age of China. This indicates that the conditions that existed prior to Empress Wu were quite positive.
By the time that Empress Wu took power, China had control over a very extensive area. It had taken power as far west as Tibet, northern India, and the Caspian Sea, as far east as Korea and sourth into Vietnam. Even areas that were not directly under Chinese control acknowledged Chinese supremacy.
Economically, China was booming as well. This was a time of greater prosperity than ever. This prosperity was both shown and increased by the canal building that had occurred by Wu's time. The Grand Canal had been built, linking the Yellow and Yangtze Rivers. This helped to bring great prosperity to China.
China at the time Empress Wu came to power, then, was strong and prosperous.