Why was the Maharal against the Sefer Me’or Einayim? Was anybody backing that Sefer? If yes, who?
Some rabbanim, like the Maharal (Be’er HaGolah, ch. 6) came out strongly against the Me’or Eina’im of R. Azarya min haAdumim, because he sometimes left rabbinic tradition in his relation to midrashim (as did the Rambam and many ge'onim), certain chronological figuring in chazal, etc. His rational and historical approach is very similar to that of the Maharatz Chayot (Chajes), and R. Yakov Emdin (who at first opposed, but later apparently accepted the book). At one point the author wrote a letter of apology and even edited some of the controversial issues (proving his positive intentions), after which the book was more widely accepted. He is cited by classic rabbinic historians, for example the Tosfot Yom Tov (Mnachot 10, 3), the Minchat Shai (Zecharia 14, 5), the Yad Malachi (Shnei haTalmudim, 12) and others. The book is not recommended for youngsters who have yet to master the "mainstream" learning, and for people who don’t have knowledgeable and well-rounded rabbanim with whom they can discuss the questions and understand both sides of the issues.