The Genius Trait on leaders worked the first time I recruited a leader. Additional leaders that I bought that had the Genius trait did not complete my current research. Seems like this Leader trait only works once.
I have found that, when you recruit a leader, sometimes the traits of that leader move to another available leader. For example, if you recruit a leader with the Genius trait which completes the current research, you now see another leader that appears to have the Genius trait. You get excited and go start researching the most expensive item you can, then go back to the leader recruiting screen and recruit that leader with the Genius trait and are disappointed when the research is not completed (yes, this happened to me!). The reason is that the leader never had the Genius trait. It just looked like he did because there is a bug that moves the icons around and the Genius icon got moved.
To test this, take a snapshot of the leader recruiting screen to get a picture of which leaders have which traits. Then recruit one of the leaders and see if the trait icons of the remaining available leaders change. It doesn't happen every time, but it happens often enough that you should catch it eventually. It is best to test when you have a lot of available leaders.
