Part of the problem is they’re being lied to on what exactly their job is. This has been reported on previously. The job description was never a soldier. It’s blatant human trafficking and slave soldiering.
Since other commenters aren’t bothering to look into it at all:
Cuba says it has disrupted a scheme in Russia to recruit Cuban citizens to fight in Ukraine.
In a statement, Cuba’s Foreign Ministry called the alleged plan a human trafficking ring. It said Cubans, both in Russia and on the island, had been recruited to fight in Russia’s war against Ukraine.