"I have no doubt that Andy will continue on with our great and lasting EPA agenda", the president tweeted.
But at the same time, Pruitt was one of the most effective implementers of the President's agenda. As Oklahoma's former attorney general, he waged a legal fight against environmental rules implemented by the agency he eventually would head. He also had a $43,000 phone booth installed in his office.
"I think the most grievous threat that we have today is this imperialistic judiciary, this judicial monarchy that has it wrong on what the First Amendment's about and has an objective to create religious sterility in the public square, which is wholly inconsistent with the Founding Fathers' view", Pruitt warned.
Later, Wheeler worked as a lobbyist representing Murray Energy and its CEO Robert Murray, a prominent Trump backer who denies the science of climate change.
Several of the allegations against Pruitt are now under review by EPA's inspector general, the Government Accountability Office and others.
"This man is directly and significantly harming my child's - and every child's - health and future with decisions to roll back environmental regulations for the benefit of big corporations", Kink wrote.
Wheeler was previously confirmed as deputy EPA administrator by the Senate through a mostly party-line vote of 53-45, with three Democratic Senators - Joe Manchin of WV, Heidi Heitkamp of ND, and Joe Donnelly of IN voting to confirm.
Massachusetts Democrats, who vocally criticized the EPA chief's actions and efforts to reverse Obama-era policies, praised news of Pruitt's resignation. In April, after Oval Office remarks in which he lauded the EPA's work, he reportedly turned to Pruitt and said: "Knock it off".
The EPA chief was not the first Trump administration official to face a public backlash at a restaurant. He rented an apartment linked to oil industry lobbyists in a pricey neighbourhood of the capital for a mere US$50 a night, a sum he only paid on nights he actually slept there.
Pruitt also rankled some Republican lawmakers, including in Midwest corn states, with his efforts to overhaul a US policy requiring biofuels like corn-based ethanol in gasoline.
"Given Pruitt's complete failure to protect our clean air and water, and with 13 open federal investigations into his work, the only question is why this took so long".