Why should we make videos that are trending?

Hey warriors.. I have heard from some people that they used to recommend to look for trending videos in youtube or Alexa what is hot section and Google trends..and they say make a video under those topics...could be a reaction video,etc..

My question is if i make such videos then what makes it linked with making money or sales? specially if the video that is trending or which i'm going to make is not related to any of the products or affiliate product that I can sell?

And also if that trending video is not under my niche of my youtube, then does making other trending videos under my different niche video channel has any good effect for my channel just because I get high amount of views to my trending video? For example, lets say my youtube channel is about Medical subjects...then if I go to youtube trends or google trends, i found out that a particular movie or about some incident is the trending topic for that moment, then if i make one of those trending topic's video, then does that has any effect if i upload such video on my same video channel where I used to make Medical videos?

Please advise... Thanks a lot!