Why no listing for Ramón Mercader/Jacques Mornard ... the assassin

It seems weird that this guy hit Trotsky over the head, and
caused his death, in Mexico. But he was only convicted and
sentenced to 20 years.

On 20 August 1940 this guy hit Trotsky from behind on the
head with an ice pick ... and Trotsky got him and subdued
him. He was convicted in Mexico in 1940 and got out around
1960 ... and then lived until 1978 until he died of cancer.

How come only 20 years for a brutal murder?

In any case I do not see a listing as to who played him in the
movie?