After reading up on the situation it's probably less to do with lithium and more with the US's "left hand shoving cocaine up our noses while right hand slaps So

After reading up on the situation it's probably less to do with lithium and more with the US's "left hand shoving cocaine up our noses while right hand slaps South American countries for making it" policy. Morales was anti-US influence, pro-coca. The right wingers and Evangelicals were against him, and Morales was socialist... basically fits the profile of exactly the type of leader the CIA would try to depose.