What make app to the "top apps"? I assumed that app is more "top" within its category mostly based on installs (quantity and velocity) and user rates and comments.
Probably also slightly some other criteria like android vitals score etc.

However, I spotted the app that is #9 in Top for parents with 1.9 average rate (sic!) from 177 users, and only 10k+ installs. All other apps in this top10 are like 100k installs and 4.8 rate. 

The question is how is it possible?
Google recently changed its ranking policy creating turmoil 

It's quite possible that what you ate seeing is a fallout of that



In the past

The algorithm Google uses is clearly not public for obvious reasons of gaming by app developers but 

Google Play help 
says


  Apps are ranked based on a combination of ratings, reviews, downloads, and other factors


I think these other factors and search query wording (apart from downloads) play an important role as explained in this blog 


  
  App Name
  App Description 
  Backlinks 
  In-App Purchase Rating and Reviews
  Updates Downloads and Engagement 
  Some Hidden factors
  


Try changing the search query significantly to see a different result.
Also the same search query from my phone and another users phone yields variations