El Greco was disdained by the immediate generations after his death because his work was opposed in many respects to the principles of the early baroque style which came to the fore near the beginning of the 17th century and soon supplanted the last surviving traits of the 16th-century Mannerism.[1] The painter was deemed incomprehensible and had no important followers[4] Only his son and a few unknown painters produced weak copies of El Greco's works. Later 17th- and early 18th-century Spanish commentators praised his skill but criticized his anti-naturalistic style and his complex iconography. Some of these commentators, such as Antonio Palomino and Céan Bermúdez described his mature work as "contemptible", "ridiculous" and "worthy of scorn".[5] The views of Palomino and Bermúdez were frequently repeated in Spanish historiography, adorned with terms such as "strange", "queer", "original", "eccentric" and "odd".[6] The phrase "sunk in eccentricity", often encountered in such texts, in time became his "madness".
Hope this helps!!!