The stereotype seems to have been around for a long time and perhaps because many learned men do concentrate so much on their work and thoughts that real life passes them by.

"The absent-minded professor is a stock character of popular fiction usually portrayed as an academic with important information, but whose focus on their learning leads him to ignore or forget his surroundings.

The stereotype is very old; a story associated with the philosopher Thales says that he walked at night with his eyes focused on the heavens, and as a result, fell down a well. [Diogenes Laërtius, "Lives of the Eminent Philosophers", "Thales"]

Examples

Isaac Newton, Adam Smith, and Albert Einstein were all considered absent-minded. André-Marie Ampère used a cloth chalkboard eraser as a handkerchief. In the streets of Paris, he mistook the side of a horse-drawn delivery van for a blackboard, began some calculation on it, walked, and then ran along beside it to continue his work when it drove off. Between the afternoon and the evening of one day he forgot a dinner invitation personally delivered by the Emperor Napoleon. Geneticist Sewall Wright, known for his copious use of chalkboards, is said to have once accidentally used a guinea pig as an eraser.

Another usage of the phrase "absent-minded professor" is common in the English language. Like the phrase itself implies, it is used to describe people who are so engrossed in their 'own world' that they fail to keep track of their surroundings. It is a common stereotype that professors get so obsessed with their research that they pay little attention to anything else."


http://dic.academic.ru/dic.nsf/enwiki/498038

I can't find anything positive about where the stereotype of Temperamental Artist although Michaelangelo was considered to be temperamental, although this may have been because he really didn't want the job of painting the Sistine Chapel.

"We have studied Michelangelo, but I haven't talked about how his personality is the model for the modern image of the artist. [pause] His paintings on the Sistine Chapel are some of the most famous works of art in the world. But, he didn't even want the job when it was offered to him—he considered himself a sculptor first, and didn't want to take time away from that. His sculpting was most important to him, and he almost refused the job. He was also famous for a quick and fiery temper, and didn't want to take suggestions about his work. He was extremely independent, fighting with powerful religious and political leaders who hired him to create works of art. So, to sum up, the modern image of the artist that we talked about yesterday is largely due to Michelangelo."

http://www.act.org/compass/esl/sample/listening4.html

Artists, have times when they really feel like painting, have great ideas and need to put them onto canvas, (or whatever) so if they are interrupted when they are inspired they would naturally behave in a temperamental way, which could lead to them having a reputation for being temperamental.