cardinals considered those nudes as immoral

Most of the people painted by Michelangelo in the Last Judgement were naked.  This is because clothes make people think of a particular historical periods while Michelangelo wanted to communicate the dramatic universal destiny of man at the end of his life, something that concerns the whole humanity. As the characters were not conceived as ideal bodies, cardinals of those times considered those nudes as immoral and obscene. Moreover, some of the characters had their back oriented towards the altar, and that couldn’t could not (this sounds like an academic work, you don't want to use abreviations like couldn't, it's that'll in academic work, you write out the whole word) really (really sounds ok but be strong in your point, the word 'really' makes it seem like you are unsure about what you are saying) be accepted by the cardinals. Nothing happened  The cardinals did nothing for more than twenty years, Michelangelo was too famous and his reputation protected him and his fresco. But some years later, with the new and severe spirit of the Counterreformation, cardinals imposed their point of view and forced Daniele da Volterra, a pupil of Michelangelo, to cover the genitals of everybody. (This is interesting and should have its own sentence) Daniele da Volterra then  so he became famous as the painter of underpants.

cardinals considered those nudes as immoral

Most of the figures painted by Michelangelo in the Last Judgement were naked. To include clothing would give an indication of a particular historical period. On the contrary, Michelangelo wanted to communicate the dramatic destiny of man at the end of his life, something that transcends any time period. As the characters were not conceived as ideal bodies, the cardinals of that period considered those nudes as immoral and obscene. Moreover, some of those characters had their backs oriented towards the altar, and that could not be accepted by the cardinals. For nearly twenty years, Michelangelo was too famous and his reputation protected him and his fresco. Some years later, with the new and severe spirit of the Counterreformation, the cardinals imposed their point of view and forced Daniele da Volterra, a pupil of Michelangelo, to cover the genitals. Daniele da Volterra then became famous as the painter of underpants.

I think Forest did a very good job. I tried improve it just a bit more.