My guess is that this is because Python is the language of choice for most academic institutions when teaching dynamically typed languages (which is something that is likely part of most Computer Science curriculums)

I think the more interesting thing here is how less popular of search term perl/php has become. I really can't find a language that is on an upward trend. Why would people be searching for these terms less over time?

EDIT: Nevermind, it's relative to all searches. More terms to search will depress these numbers.