Evo Morales was probably “helped” to “resign” by the US government. From Caitlin Johnstone at medium.com:

There has been a military coup in Bolivia backed by violent right-wing rioters and the US government, but you’d hardly know this from any of the mainstream media headlines.
“Bolivian President Evo Morales steps down following accusations of election fraud” proclaims CNN.
“Bolivia’s Morales resigns amid scathing election report, rising protests” reports The Washington Post.
“Bolivian Leader Evo Morales Steps Down” says The New York Times.
“Bolivian President Evo Morales resigns amid fraud poll protests” declaresthe BBC.
“President of Bolivia steps down amid allegations of election rigging” we are informed by Telegraph.
“Bolivia’s President Morales resigns after backlash to disputed election” saysthe Sydney Morning Herald.