Tesla success with mass manufacture the Model 3 highly profitably in 2017/2018 was a huge shock to the infustry. Nobody thought it was possible and it lead to a huge increase in investments.

And even then the base from where these investments sarted was massivly higher because all companies had increasingly experimented with EVs. The Roadster making EV cool and desirable and the Model S really showing what a modern car was.

Battery investment doesnt come from knowwhere either. You need products that actually allow for continues battery scaling. Tesla investing huge amounts into Giga Nevada was necessary to build batteries in these quantities. And the other battery companies took note and also started to think way bigger.

Those battery factories is what allowed for things like the Model 3. Consumer electronic alone wouldnt have driven battery demand so agressivly since the Model S. Battery improving comes from increase investment and research drivien by expectation of growth in the demand. And Tesla unquestionably was the most important driver behind the believe in future demand.