It's mainly because that length allows for a well-developed plot and character arcs without being overly long or dragging on.
Well, 100,000 words gives authors enough space to tell a complex story with depth and detail. It's not too short to rush things and not so long that it becomes overwhelming for readers.
Chapter 873, "The Sooner, The Better", is the clearest early answer because it turns Wan Jia's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Under a curse?!" Wan Jia stood up excitedly.
The best chapter pointer here is Chapter 31, "Master, I've been having some bad luck lately!". It opens with Before Shen Lan had reached the backyard, she already heard the sounds of... and closes on After staying in the study and reading for another day, she finally....
The best chapter pointer here is Chapter 14, "She Looks So Cool Dancing with a Gun". It opens with Lin Manru had a rare good night's sleep. and closes on But clearly, Lin Manru was unable to accept that her delicate daughter had....
Chapter 734, "Are These Primary School Students Arguing?", is the clearest early answer because it turns Shu Yue's situation into a concrete plot event. Early on, Old Sir Jiang was especially happy.. By the end, Jiang Yan had to return to the set as well..
Chapter 836, "It's been a long time since I last saw Jin Siyue", is the clearest early answer because it turns Gu Yu's situation into a concrete plot event. The chapter turns that into something concrete by moving from You!" Rong Junsheng seemed to have heard the commotion over here and...
Chapter 766, "Young Master Gu, Please Come Inside!", is the clearest early answer because it turns Zhao Lang's situation into a concrete plot event. The chapter turns that into something concrete by moving from Young Master Gu!" Rong Kexi instantly put down her phone and rushed...
Chapter 13 is the strongest chapter-level answer because it starts from Sensing that something was off with Jiang Yan, Jiang Yan dismissed the... and follows through on How could this happen..." Lin Manru didn't want to hear any more of her....
Chapter 592, "The Secret of Dragon Ridge Lake", is the clearest early answer because the hidden truth stops feeling like mere subtext. The chapter turns that into something concrete by moving from Hmm?" Jiang Li's unexpected question left Zhao Lang somewhat...
Chapter 913, "Call Me Daddy", is the clearest early answer because it turns Jiang Mingchuan's situation into a concrete plot event. The chapter turns that into something concrete by moving from Meng Wanzhi woke up early, preparing to get the two little rascals up...