Wolfgang Bernhard – the head of Daimler Trucks & Buses and a member of Daimler AG’s board of management – resigned last week “at his own request and for personal reasons,” according to the company.

In a statement, Daimler AG noted that Bernhard “has been released from his duties with immediate effect” and that Dieter Zetsche will head Daimler Trucks & Buses until a successor is appointed.

Bernhard leaves big shoes to fill on the commercial vehicle side of Daimler AG’s business. He took over the Mercedes-Benz Vans division in 2009 and then was tapped to join Daimler AG’s board of management in February 2010.

Until March 2013, he served as the board of management’s member for production and procurement at Mercedes-Benz Cars & Mercedes-Benz Vans before taking over as head of Daimler Trucks & Buses in April 2013.

Bernhard had championed a variety of different initiatives at Daimler AG, including the connected truck, which he believed needed to be “opened up” amongst the world’s truck makers.

“We need open platforms eventually to make connected truck platform valuable to customers,” he said during an event at the company’s headquarters last year. “We have to open it to everybody.”

He also believed that diesel power would remain “the most important ‘alternative’ in the United States” in terms of truck power for some time to come.

“We still have 200 times more diesel stations than natural gas stations, and engines must be up for the task of hauling long distances,” Bernhard explained in a speech a few years ago. “My alternative fuel is diesel because I don’t see any replacement for diesel in the long run.”

He also called for more “sensible” regulatory policies in the U.S. as well; a position that subsequently has become a major policy theme of the Trump administration.

“If the EPA [Environmental Protection Agency] goes beyond the point where the customer is willing to pay for it, we are making a mistake,” he said. “The customer’s payback for buying new technology needs to be around 18 months. We should push EPA to use this rule of thumb and make sure we aren’t doing stupid things.”