Anglic is not German though. Nor is Frisian, Dutch or Low German. Don't confuse German with Germanic (which is an even bigger family of languages containing also Swedish etc.). Only the right half of your Diagram is actually German.

The split happened during the second Germanic consonant shift in the 6th-8th century, where the speakers south of the Benrath line shifted their k' to ch's and their t's to ts's. In English it's make and what, in Dutch and Low German maken and wat**, whereas in Standard German it's machen and was** and in Bavarian macha and wos. Only Languages that made that shift are considered German.

That doesn't necessarily mean that, for example, English and Low German are more similar than Low German and Luxembourgish. The whole area is part of the Continental West Germanic continuum and the closer you are geographically to someone the more likely you can understand each other. I the past it was much more usual to match and mix these languages to your needing. It was more important to be able to speak with the people from the neighbouring village than someone at the other end of the Holy Roman Empire, so someone speaking a German dialect in Cologne would be much more likely to understand someone speaking Düsseldorfer Platt (A Low German dialect) than someone from Graz even though they were both speaking "German".