I don't think anyone is able to learn many languages very easily. If you want to have meaningful discussions in a language you need a vocabulary on the order of 5-10k words depending on the subject and how much exposure you have, which is a cool year of study for even the fastest learners and more akin to 2-3 for us mere mortals.

Most cases of people speaking 10+ languages lean heavily on speaking many closely related languages in a family, which most people already cope with pretty well.