What is the main difference between main idea and theme?

there isn't a difference

theme is the universal message and main idea is the plot.

the theme is the plot and the message is the main idea.

He "crushed" over your feelings when he told you he didn't want to go to the dance with you. it made you feel crushed or dumbfounded that he declined. the girl had no words.i don't even know if this but i hope it does.