Game Theory and Blackmail of Politicians

The FBI had highly incriminating tapes of Martin Luther King indulging in adultery, dirty jokes, etc. This was illegal, I think, since it was not taped at his office but at home or sleeping place, so it has been suppressed by court order till 2027.

Why, though, didn't the FBI leak this information back in 1964? I can think of two reasons:

1. The FBI really wasn't trying to snoop on King's personal life. The FBI was just doing its job, checking out his communist connections, and having found that though he did consort with communists, he wasn't one, they figured their job was done.

2. The FBI (i.e., J. Edgar Hoover) blackmailed King, somehow changing his behavior.

I don't know why the FBI would like to blackmail King, but if you think J. Edgar Hoover was anti-King, reason 2 is your only explanation. If he was anti-King, why didn't he leak the adultery info-- or somehow set up King to be exposed by a third party?

Reason 2 might be verifiable. After the dates when the FBI adultery tapes were made, did King somehow change his behavior?

The idea of blackmail is important in other contexts too.

1. I had the impression that Dole was going easy on Clinton in the 1996 campaign. Was this because Clinton had info on Dole?

2. Rep. Rangel has gotten away with tax evasion for years, it seems. Did presidents use his vulnerability to prosecution to get him to be cooperative on tax policy?