It looks like "How" was accidentally dropped from the title so as-written it doesn't quite make sense because today Guernica is hardly considered a "flop". His related sketches The Dream and Lie of Franco[1][2] are also worth a look.
Fun fact: Franco wanted Guernica exhibited in Spain but Picasso refused. It lived at the MoMA with instructions that it shouldn't be sent to Spain until Spain was a democracy and the people were free.
Not so fun fact: Picasso was an arogant asshole of the highest order.