there is no reason to say bitcoin is bad for the environment, only some people say bitcoin is bad for the environment, bitcoin has long been founded by satoshi nagatomo, why only now there are so many debates like that, if bitcoin really damages the environment why not prevent it in the first place..
Most times the people who says bitcoin is bad for the environment say it out of ignorance, most of them have little or no understanding about bitcoin and possibly just take any Damn bad news there hear about bitcoin. I can proudly say bitcoin adds value to the environment, check out in some countries where there are lack of job opportunities, crypto trading and investing in bitcoin serves as a self employment to their citizens thereby reducing the rate of poverty.
cryptocurrencies don't harm the environment like you said. With the existence of cryptocurrencies some of them have reduced their actions in the environment, some of their time is just to monitor the future growth of the market. On the other hand, they have indirectly increased the economic growth in the environment they live in.