BBC News as usual reporting very selectively on Cuba

The last sentence of this BBC report http://www.bbc.co.uk/news/world-latin-america-33398655 on a rare Fidel Castro appearance is incredibly one-sided even for the BBC.

'Relations had been frozen since the early 1960s when the US broke links and imposed a trade embargo on Cuba.'

Why did the US break links and impose a trade embargo? Was there no cause? For the lefty activists at the BBC facts as usual are subservient to a cause.