As with Elon, its not about a matter of fact. Elon knows this, it was likely pressure from his shareholders that forced the Tesla announcement of dropping BTC purchases. Elon I believe has been on record stating he believes Bitcoin incentivizes green energy, although don't quote me on that.
The Tesla movement was clearly a PR move, rather than Elon suddenly developing a conscious, and changing his mind with Bitcoin. I also believe he's been talking a lot about Dogecoin...so there's that too.
Perhaps. Don't forget he has done a few dubious things to his own company and told everyone he thought Tesla was overpriced.
The thing is, we don't need to prove that all miners are on green energy. We just need to show that there's a concentrated effort for them to mitigate. We might know that lower the costs, the more profit margin for the miners, so of course they aren't going to use fossil fuels for no reason, but we aren't the people that need convincing. Its the general public, and if we can refute their claims, via providing a small percentage of miners, that have openly declared what they use as evidence to back it up, I believe that will only be beneficial.
I doubt miners actually care about using renewable or sustainable energy at all. Economics of mining makes it such that miners will always choose the cheapest energy source there is. Miners don't have to care about using it either, it doesn't influence the price. They're doing this to appease Elon and to hopefully pump the price up further. There isn't any conscious effort for miners to mitigate, or at least the majority of it, instead it'll be more accurate to say that they're always mitigating to a cheaper energy source. Trying to greenwash people by telling them that a few companies are environmentally conscious wouldn't actually do enough but we'll see the results regardless.
Nothing will ever solve the problem with ewaste anyways, there is no going about that. Electrical usage is hardly a significant issue in Bitcoin.