Researches from pokestops

I am trying to finish let's go melting and I'm stuck on 1/2 anorith and Eileen

I check leekduck and I found out that the "make 3 great throws in a row" yields to these 2

Now its been a while I play daily and I have seen only one, is there a reason why this research is extremely rare?

Is there something I can do to snipe that research and find it on a pokestop? Or is it just rng?