The difference is that collusion between banks is cartel price fixing and is very illegal. The majority of reported cases of traders requesting rate moves did not fall into this category unlike the Hayes case.
For the cases where the traders were just asking their own setters to move the rate, there was no collusion. They work for the same company and not even in separate, Chinese walled departments.
Also, in the intra-bank cases, I don't recall seeing any where the setters were actually breaking BBA rules. The problem was that the rules were meaningless when there was no uncollateralised borrowing.
> I am not sure the impact on the market was nefarious
You're making a lot of assumptions. What is clear is that the interventions were material and directional. And that would have had an effect on both institutional and retail customers. That's usually the time when regulators get all medieval.
There was a move towards collateralised transactions so the overnight rates become more important for funding than the unsecured rates.
On the low balling, interestingly I am not sure the impact on the market was nefarious. It was certainly material but I do not believe that when borrowers and lenders referenced Libor in their loan contract, they really meant to index their interest rate paid on the 3 month credit risk of a bank. I think they did on the assumption that large international banks had near zero credit risk for 3 months borrowing (which was true until 2007) and that Libor was a convenient way to measure a 3 month risk free rate on top of which they would add a credit risk margin. When Libor started shooting up in 2008, it was not because of the general levels of interest rates (central banks were slashing interest rates at the same time) but because of bank credit risk. So though contractually borrowers should have paid a higher interest rate during that period, the low balling probably had the effect to make the interest rate closer than what borrowers and lenders probably intended when they referenced Libor in their contract.