Some facts I didn't mention:

-Our foreign service was informed by the opposition of their plans on Friday prior to the uprising
-Several high ranking officers were on board the plot, but due to it happening before the planned date they waivered. Maduro has now begun a purge, starting with the head of Sebin.
-Maduro was on the airport and about to run off from the country when Russia intervened and ordered him to stay
-Russian planes have recently landed in Caracas

Caracas Chronicles has daily information on what's going on.
https://www.caracaschronicles.com/2019/04/30/the-few-known-facts-of-april-30th/

Report on Cuban boots on the ground in Venezuela:
https://panampost.com/josefina-blanco/2019/02/20/proof-of-extensive-cuban-military-presence-in-the-venezuelan-armed-forces/
tl;dr- at least a hundred thousand Cubans have been deployed by their government to Venezuela. Besides aid workers they include 9 battalions of infantry, special forces and a number of high-ranking officers. They are embedded within the military hierarchy and enforce loyalty towards the regime. This presence dates back to the times of Chávez.