"Because Sherlock Holmes is a great man. And I think one day - if we're very, very lucky, he might even be a good man." -Lestrade in 'A Study in Pink'
This is what this season was about - Sherlock becoming human again, the only thing that was missing from a truly epic story told over the span of four seasons. In this mind numbing psychological thriller, the brilliant acting and inspired direction is only surpassed by the emotional undertone that makes Sherlock find his humane touch - something that he had locked away somewhere within his psyche since his childhood. But that humane aspect of Sherlock's character, though not superficially apparent, always found expression in his love for Dr. Watson and Mary, more so than ever in this season of this epic series. Truly, as Mycroft explains - the man Sherlock is today, is a result of memories suppressed and modified and of deep seated psychological trauma.
Why then is he a sociopath and not a psychopathic villain like Moriarty or Culverton Smith? Because, he was always a good person deep down even though he did not know about it himself. The finale does a stunning job at giving us an insight into his past, and his troubled childhood, while at the same time giving us a glimpse of his genius intellect as in other episodes. It's a shame that some people are criticizing it for being overtly about psychological twists and less about solving crime. I ask them if they ever truly would have been satisfied with 'Sherlock' if there had been so many unanswered questions at the end of what could well be the last episode ever for the series. This was a story that needed to be told - and told it was, in the most magnificent and epic way possible - something that is well captured in the following quotes near the episode end:
Police Officer - "He's a great man sir."
Lestrade - "He's better than that. He's a good one."
As Mary put it aptly at the end - it's all about the legend, the stories and the adventures - a story that might well be the greatest detective story ever told!