http://www.cubadebate.cu/especiales/2012/04/11/la-llamada-de-fidel-a-chavez-el-12-de-abril-de-2002/
And this is from Randy Alonso Falcón, a Cuban journalist, caught in the middle of those events, helping Chávez's daughter to counter the propaganda coup, while Fidel threw his weight in all directions trying to help organize the counter-coup in Venezuela:
http://www.cubadebate.cu/opinion/2012/04/11/una-llamada-crucial/
Of course, the main factor was the existence of popular support (and significant support in the armed forces) in Venezuela, but in volatile moments like those, the role of a figure like Fidel cannot be discounted, as small things turn out to have extreme consequences.
PS: Use Google Language Tools if you cannot read Spanish.