In fact, AT&T agreed not to enter the computer market in return for being allowed to maintain a monopoly. They agreed to the 1984 breakup only in return for being allowed to make computers - a decision which did not go well, since their computer line was never very successful.
In terms of strategy it's not a bad move though, after all the computer (and by extension the smartphone) did become the new telephone. Pretty much all phones even run an OS with Unix-like underpinnings.
They just failed to capitalise on it but it was a pretty good vision IMO.
In 1995 I was an intern at Indosat, a telephone company in Indonesia.
Indosat bought billing system from ATT and also some PCs from them (maybe the PCs were part of the deal).
That is how I experienced the speed of a Pentium PC for the first time.
