To begin let me caveat that I'm a huge proponent of environmental regulation. That said, most of the regulations Trump is rolling back aren't longstanding ones that produced the cleanups you observed. They're ones the Obama administration rushed through in the last year or two of his presidency, which often had quite sweeping effects or federalized things that had previously been regulated at the state level.

These methane regulations are a good example. Every state that has oil & gas drilling already regulates methane emissions as part of the necessary permits. The Obama EPA enacted a rule to federalize those standards that took effect in March of 2016. It's a duplicative rule that's been operative for about five minutes.

I like Obama a lot, but on the environmental front, he was willing to spend zero political capital to achieve consensus on environmental reforms. To the contrary, he won reelection on a pro-coal and pro-fracking platform! Here is Obama criticizing Romney for standing in front of a coal plant (as Governor) and saying "this plant kills": https://www.youtube.com/watch?v=YXRmlxBDjfE. Here is Obama talking about the how great fracking is: https://www.youtube.com/watch?v=7uVGY3sIBsA. He somehow found environmental Jesus around 2015 and rushed through a bunch of regulations at the last minute. But, as such, his successor is perfectly entitled to reverse them just as quickly and easily.