It's not complicated.
A left wing government in Latin America uses natural resources to benefit poor/indigenous people. The military installed a right wing government to make sure that those natural resources flow cheaply to businesses in the global north.
This is as generic of a coup that you can get. The only twist is that the resource in question is not petroleum. Instead, the resource in question is lithium which powers Tesla and iPhones and therefore a lot of liberals in the global north approve of this.
Obviously there is complexities in the political situation in Bolivia but it doesn't change the salient fact that the military intervened and installed a right wing government. In every country where there is a coup, there is always domestic opposition to the left wing leader who gets deposed. This is to be expected, no country has perfectly clean elections and 100% support for its leadership. If 2019 in Bolivia is not a coup then neither is Iran in 1953 nor is Chile in 1973.
One more thing, elections are secondary to who controls the resources when we are assessing how democratic a country is. If there is choice between perfect elections but a few people own all of the wealth or a country with imperfect elections but the people control the country's wealth, I'd take the second option.
Evo might have been degrading elections in Bolvia but he most certainly was degrading the Oligarchy and centuries of colonial extraction and white supremacy in Bolivia and that is why the power brokers in Washington, Langley and Tesla's boardroom decided that he needed to go.
Evo is not just degrading elections. The was a national vote on whether he could run again and he lost. He didn't accept those results so he used the courts that he filled to subvert the will of the people. He had no business being on the damn ballot.
The election comes and it a complete undemocratic joke, so of course no one will respect those results. They were not just imperfect, they were clearly corrupt and should be seen as invalid. Protest of course break out, and this fool wants to hesitate calling new ones and resigning, which would have been the right move.
I don't support the right wing, but if the cops and armed forces would have done the opposite of what they did, quell the protest and stand behind Evo, then that would make him a defacto dictator.
Evo should have groomed a successor what would carry on the work instead of trying to finesse the system. His undemocratic moves were not to serve the indigenous people, it were to serve himself.
All you are doing here is saying Evo's undemocratic power grab is more acceptable to you than the right wing's.
I find them both vile, that's while I call it complicated, because I don't want to hand wave **** to make my argument more convenient to make.
But somehow to socialist, not caping for Evo's corrupt *** means you support the buffoonery for the other side. It is complicated because Evo's own actions lead Bolivia down this road too. So while of course the military telling him to leave surely smells like a coup, part of what could have motivated that was Mendes' own undemocratic actions.