Hi, I can answer that question. During Sam & Friends and well before that Junior Good Morning Show, there were several reasons why he started puppetry.
(1. To get a job working on television
(2. A way to help fund his way through College
(3. To experiment with art and the film medium.
Jim went to Europe and left Jane and Bob (Forgot his name) to making more Sam & Friends' episodes without him. Jim was always an artist, but he mostly did print art like having a little side poster business I think during his college years as well as being the cartoonist for his college paper. Jim traveled and to also I think clear his mind on what he was going to do with his life in terms of a career. He didn't think much of being a puppeteer. Then he seen adult puppetry for the very first time, from my research there was a couple of really risky adult content as well as some satire that Jim must have seen at a certain show. I forgot what show it was but Jim was amazed that here's full grown men performing puppets as a career. So Jim thought of what he was doing with art and the television medium and thought, perhaps there's something there he could do more of. And to my knowledge, became history.
"The truth of the matter is that the frog is a great deal more interesting to look at, and who notices what the bearded man is doing?"
lol World of Jim Henson, I just bought the rare VHS of that recently. Anyone know when that footage originally came out? Not WoJH (that's 1993 right?) but the Jim Henson / Kermit interview? Looks late 80s.