Probably just the product of people copying what's popular and so on, with the community getting saturated with it and covering the new stuff. This isn't isolated to web novels. Hollywood keeps making reboots or sequels or prequels of what's popular. Saw franchise has 10 movies.
In my country, cheap coffee shops are the craze. One shop opened advertising cheapest coffee at 39 pesos. The name was something with 39, I can't recall exactly. Then another shop opens with 38 pesos coffee. Then another with 37. No joking, in one small town, there were shops named 39, 38, and 37 near each other, all selling coffee. Plus other coffee shops too. I look around and think there's nothing new. People just want to be safe with their investments (including investment of time to write).