I was working on a different project and I came across some data to visualize. I didn't think it was worth starting up Excel or google sheets. I just wanted to see a histogram of a bunch of numbers.
I figured there was a number of online tools to visualize data, much like there's web-based tools to edit images, create gifs, host images, etc. But to my surprise I couldn't find any. I tried wolfram-alpha and tried "plot [data]" but that didn't work as well.
I also remember having discussions online in which I wanted to share some data to resolve a dispute. What I would normally do is do a google image search to try to find some chart (e.g. "taxes as a percentage of gdp"). This was hit or miss and often resulted in outdated data, inscrutable sources and suspicious websites.
That's when I had the idea that I should build a platform to create a host charts. This was the birth of Chart It.