1. Rivaling the pyramids of Egypt or even the ancient cities of the Maya as an achievement, the army of terra-cotta warriors created to protect Qin Shi Huang, China's first emperior, in his afterlife is more than 2,000 years old and took 700,000 artisans more than 36 years to complete.
2. Digging the sediments in northern China, scientists have gathered evidence suggesting that complex life-forms emerged much earlier than previously thought.
Question: Although both of the sentences have started with dangling modifier, why the second clause of the first sentence has taken a passive subject (the army of terra-cotta warriors) and the second clause of the second sentence has taken an active subject (scientists)?