You missed out that the breach of the law committed by the leave campaign was because they took advice from the Electoral Commission, who stated that what they were going to do (in general terms) was legal, when, in fact, it was not. And that the Electoral Commission then attempted to cover up their own part in this to the High Court.
From the High Court ruling:
94. For the reasons given, we conclude that the Electoral Commission has misinterpreted the definition of “referendum expenses” in section 111(2) of PPERA. The source of its error is a mistaken assumption that an individual or body which makes a donation to a permitted participant cannot thereby incur referendum expenses. As a result of this error, the Electoral Commission has interpreted the definition in a way that is inconsistent with both the language and the purpose of the legislation.
So the Electoral Commission have found the leave campaign guilty of serious crimes, but the High Court has found the Electoral Commission (in effect) misled the leave campaign, causing that breach of the law.
There have also been numerous accusations of breaches of the rules by the remain campaign which the Electoral Commission has failed to investigate (not investigated and found to be unsubstantiated, but failed to investigate).