In some countries one personal investigation would make a minister resign, Scott Pruitt had 14 and expected to survive them all, however he has finally resigned.
Given Trump, and some of the clearly incorrect things he has said about the environment, particularly about how climate change was invented by the Chinese to give them an advantage, I think any sensible movement in American public policy on climate change and reducing carbon emissions will not happen while Trump is in the White House.
Because of these views I find it highly unlikely to get sensible EPA Director under Trump. The temporary Director will be Pruitt’s Assistant Director Andrew Wheeler, a former coal lobbyist. This doesn’t sound like an improvement, particularly as coal use needs to largely disappear, but we will wait to see how long he stays and what his policies are – he would struggle to have worse judgement than his predecessor Scott Pruitt.