There's no evidence that Snowden brought his supposed 'concerns' to anybody in his chain of command, prior to defecting to Russia. The documents he began stealing in 2012 weren't targeted towards the bulk data collection program - he exfiltrated whatever he could lay his hands on, which of the hundreds of thousands of items were mostly military secrets, and classified information on intelligence work abroad. The claim that this was all driven by watching Clapper testify in committee is a convenient lie, a cover-up for what he was really doing: a massive theft of secrets across the board.
Serial liars do often go back and 'clarify' their lies once called out, it's part of spinning a web of deception. Admitting any wrongdoing, as normal people might do, isn't on the agenda for people like Snowden, all puffed up and full of ego, living off their own bullshit.
Not only did he defect to Russia and enjoy being celebrated there, he also has many people in the US and allies lauding his espionage, filmmakers and journalists gushing over his narrative and airbrushing out inconvenient facts. What a series of accolades for a liar and thief. He seems to revel in this 'wise whistleblower-in-exile' act he's carved out for himself while remaining Putin's pet. This treacherous escapade worked out better than he ever could have imagined.