Because it's virtue signaling. They aren't environmentalists.

Environmentalists don't buy new items, they try to reduce and reuse. So they will ride a used bike while owning a used car. They don't buy a Tesla to show the world how green they are.

Environmentalists don't believe in mass migration due to the carbon footprint. They encourage the use of local resources and local leadership. They don't think flying and boating people using disposable products and processed foods is good for the planet or for those humans migrating.

These so called environmentalists are also the same people that think an indulgence tax on carbon absolves them since they feel they can afford it, and that means everyone else can too. And that a tax is revenue neutral for a government.

Tl;Dr they are idiots