Riding high on the hype wave of its forthcoming streaming service HBO Max, AT&T probably wasn’t expecting to be brought back down to earth with a thud this week, which is what happened after an activist investor with a substantial stake in the business echoed what we have been saying for years – imploring AT&T to sell the self-imploding satellite TV business. This lambasting is arguably more embarrassing for AT&T than its last quarterly results filing, and we have seldom seen such an outright public hanging of a mammoth company by one of its own stakeholders. Imagine your company making such a calamitous misjudgment that a minority investor, fraught with fears about sustained incompetence and contempt for trends, is driven…