Libor is just structurally insane, and basically designed for abuse. This isn't to say that they should be absolved of responsibilities, but Libor (and equivalents elsewhere) should be redesigned to reduce the opportunities for collusion.

There have been prosecutions in the US and UK.

Read the Gervais Principle. You don't get to the top by leaving a trail of document-able shady decisions.

The Serious Fraud Office has said it's individual prosecutions will be announced in the next few months.