Complex sentence: To the Sandinistas, Fonseca was considered a "modern Sandino", at times he over looked the importance of obtaining support from the urban revolutionaries (Humberto Ortega), at the same time his loyalty to the peasantry could not be questioned.
Split into simpler sentences: To the Sandinistas, Fonseca was considered a "modern Sandino". At the same time, his loyalty to the peasantry could not be questioned.