Board Thread:Questions and Answers/@comment-5441128-20170719132231/@comment-24152851-20170725115230

I listed all those sites stating Grodd as "fan favorite" or "popular".

He's popular because of memes, he's funny, he's an impressive CGI effect, he was one of the first Flash villains aside from RF to be genuinely terrifying, he completely overpowers Barry whenever they one-on-one battle (not even RF stomped him that badly).

If you still don't understand why Grodd is popular, I don't really know how to explain it. Just accept that he is.