Before Dieselgate they were moving at compliance pace and still insisting that diesel had a role to play. Although other governments were supportive of electrification (particularly of note were the 2nd and 3rd largest European markets in the UK and France, both of whose large capital cities have terrible air quality), the German government didn't provide support.
Post-dieselgate diesel car sales have collapsed in the major diesel markets, including in Germany. (Sales are down anyway, but diesel car sales are down far more than gasoline car sales). The German manufacturers had diesel as a competitive strength, but the value of that strength is greatly diminished, and it has pushed the German manufacturers to accelerate their electrification programs.
Meanwhile, in the USA, the result of Dieselgate is a multi-billion dollar investment in CCS charging infrastructure, with a little additional CHAdeMO support. Although more limited than the Supercharger network, it will effectively lower the cost of comprehensive coverage, providing additional help to competing manufacturers, who will find it easier to sell their BEVs, whether they are serious about scaling or they are just going to do what's necessary for regulatory compliance.
In my opinion, Dieselgate has increased competitive pressures on Tesla by forcing the hand of German manufacturers, and encouraged China aggressively to pursue electric vehicle manufacturing as a major export industry.
All valid points, however, I don't see them materially affecting Tesla in a negative way.
Tesla is a member of CCS, so there should not a barrier to that network supporting Teslas.
Manufacturers still need to build the cars (low volume of competition).
EVs are replacing ICE, so the customer pool is large and growing. It is not EVs fighting over a small (EV-only) market segment.
Currently, Tesla is supply constrained, and more people need cars that they can supply, having other sources of EVs is good for the Earth, and EV adoption in general.
Tesla/ ELon never wanted to be the only EV manufacturer, and I think he is disappointed other OEMs haven't moved faster. Ultimately, that delay may cost them dearly (but that is a different thread).