Yasuo has 3 skins and a base skin and has been out for roughly 3 going on to 4 years. Yasuo is the most popular champion by a large margin, as stated by Kindlejack, while Malzahar isn't the most popular, but hasn't had a skin in 4 years. Personally I want the Yasuo skin and a secondary skin to go to Malzahar, but which would you prioritize for getting the skin? The most popular champion vs the one who hasn't been addressed in 4 years?
Malzahar got a skin in Snowdown of 2015 2014.
It would seem to me that the most money could be made in the moderately played champions. The champions who are starting to see more play, but aren't on the level of Yasuo. The vast numbers of Yasuo players have likely already purchased a skin for him and are less likely to buy another one, where champions like Taliyah with only one skin but a fair number of players might sell more skins...but I am certainly not an expert and I'm sure Riot has far more data to draw conclusions from than I do.
