Why? There's nothing wrong with moving onto other things and pursuing other interests, but she has this perplexing perspective (which you echoed in this statement) that somehow the 'shitty robots' content was something to look down on. It was good stuff, and if she wanted to continue, it would have been perfectly fine and something you could build a career around.
However, it can at the same time be true that they represented her own fear of failure, and were holding her back from actually fulfilling her real potential.
Of course she can make better actually functioning robots than I can.
“it was harder and harder to come up with ideas. I was always concerned that it was eventually going to be like beating a dead horse, and that the joke was going to be over and I didn't have anywhere else to go.”
The part that's perplexing is why she (and some others) see that content as somehow beneath her and why she has this general negative and insecure attitude towards the "shitty robots" content she created. That content entertained a lot of people and allowed her to stand out from the mass of other Youtube content creators.