Elmo talked to children like babies. Before elmo, Sesame Street treated children as adults. They still do at times.
With Norah Jones: https://youtu.be/FEzxchU4RUY
With Katy Perry: https://youtu.be/PwZnCkoX5gI
And my absolute favorite, better than the original, with the Goo Goo Dolls: https://youtu.be/uGohKgNOXnU
Edit... but... yes... the Elmo Numa Numa tops everything: https://youtu.be/2rAKszSX2tU (which btw, was indeed uploaded 11 years ago, but I think has an erroneous view count..)
My guess is they are trying to generate much-needed funds from toy sales, as well as compete for eyeballs with other more engaging children's programming ("bombardment" as Fred Rogers once called it).
The Corporation for Public Broadcasting is also a non-profit, funded solely by the federal government, but is independent from PBS and doesn't produce any programming.
https://en.wikipedia.org/wiki/List_of_Sesame_Street_Muppets
Here's Johnny Cash on Sesame Street: