Obama tightened offshore drilling regulations after a the 2010 Deepwater Horizons oil spill in the Gulf of Mexico, which resulted in 11 dead and 200 million gallons of oil being released.

Since taking office, Trump steadily undid various regulations on offshore drilling. The changes included relaxed testing requirements on equipment, decreased frequency of visits by inspectors, and eased safety requirements during active production of oil or gas.

Trump also disparaged renewable energy sources, including claiming that windmills cause cancer. His administration has rolled back several other regulations, including for endangered species and coal pollution.

NPR – Trump Administration Moves To Roll Back Offshore Drilling Safety Regulations
Time – The Trump Administration Is Rolling Back Offshore-Drilling Regulations
The Hill – Trump officials ease offshore safety rule
The Hill – Trump administration eases Obama-era offshore drilling safety rules