Bolivian here. It's mostly a sub product of catholic syncretism. Since Spain colonized the area now known as Bolivia the indigenous population was exposed to the strategy of combining Spanish and native beliefs in order to make Catholicism more appealing to the conquered nations. Part of the strategy was to associate indigenous heroes or gods with catholic saints and this practice was super effective. Fast forward some 300 years into the future. The indigenous population of Bolivia (which is more than half the population of the country) is not taken into account, and indigenous people was considered second class citizens, just a little above domestic animals...and this worldwide known freedom fighter comes to the country to change things. Ok, he failed and now is death, but hey, his soul may be listening. What if I ask him to help me with the rains this year? Oh my God, it's raining! I must tell my friends so they can pray to him to. I must add that Che Guevara's case is not unique, many political figures and even big time drug dealers receive this treatment as well.