If I have got it right, measles is not the main threat, but complications. And being well nourished won't prevent the complications.
One of the most common complications is diarrhea, but luckily in rich countries it won't be fatal, though in poor countries it's a serious problem. One of the main reasons why measles is rarely deadly in the western countries. However, even in the west, brain inflammation is a danger, even though it's rare.
yes, you've got it correct and even our western Doctors beleived in fighting the fever which is excatly what was needed and created more problems but that was in the past. Old Knowledge...