IIRC, Bell ended up wanting to spend his life after inventing the telephone as a scientist and a researcher, rather than tending to the running of Bell Telephone and AT&T.
Well, it's a (usually believed for nationality reasons) myth that Alexander Graham Bell invented the telephone.
In reality, it was the German "Philipp Reis" who invented it. In Friedrichsdorf he made the first prototype and also invented the special (coal based) contact microphone used in phones ~ 1990. He demoed the prototype in 1861 before the physical society in Frankfurt/Main.
Later on he sold phones in quite low quantity, usually to experimenters. Examples of the phones made it as far as to Russia or Scotland. Bell, who was too from Scotland, learned about Reis' telephone in Edinburgh in 1862.
Bell reverse-engineered it, improved it, and created a successful business around it. And that's not something shabby...
... but he definitely didn't invent it. Not even the name. "Telephon" was the name that Philipp Reis already used.