And they do so because German car manufactures weren't interested in building an electric delivery truck for them...

Which shows that Tesla is not the only new player in town.

Given that much of the value chain isn't provided by OEMs anyway, commercial vehicles (where comfort and optics aren't as important) can be produced without the help of an OEM.

Which also goes to show how ridiculously easy an electric vehicle is to produce, considering there isn't much to the engine nor transmission (the two most complex items) necessary.