I'm sure the environmental impact of ditching lightning is mixed. On the plus side, long term, having everyone on the same connector is good in lots of ways. In the short term, it's disruptive. It also makes it easier to switch between platforms or live in a multi-platform household; this is good for people, and might be good for Apple or might not.

There's a reason Apple waited 10 years to change on iPhones, even though they switched to USB-C on other products.

They could have potentially had both ports, but nobody seems to want to put two ports on phones, and Apple is not one to put an old and new thing together.