What was the content of your videos?
If it was from someone well respected in academia, you could say something like, "After listening to lectures made by Joseph Stiglitz, I became interested in the detrimental effects of asymmetrical information."
Or, if it was from those YouTube bloggers, you could say, "I became interested in studying mathematics after I saw a mathematician explaining in terms of mathematics how Legolas, a character from Lord of the Rings, could exert superhuman powers. The use of a concrete discipline to answer unconventional questions has given me a passion to study Maths at a university level."
Basically, spin it so seems lofty. Of course, take my advice with a grain of salt.