"This morning I ate breakfast quickly because the train was late." "I ate breakfast quickly this morning because the train was late." "Because the train was late I ate breakfast quickly this morning." "This morning, because the train was late, I was breakfast quickly."
I feel like the first two are pretty much the same. However, the third sentence emphasizes that the train was late, and the last sentence emphasizes that the event happened "this morning".
Is there a linguistic rule that explains why ordering a sentence in a particular way can change its emphasis or connotation?