I think it's not the main problem and reason,First of all governments can not control cryptocurrencies emission,despite the fact that usually there is limited supply and cryptocurrencies are making emission with mathematical algorithms and not by central administrators and central banks.So just imagine how much electricity do they need,For example let's get bitcoin,Bitcoin's energy usage is very hug(For example as I remember correctly in Iceland bitcoin miners used more electricity than citizens for their daily need in one year).This is a very complex issue and needs distinctive approaches,Special structures must consider every details to do something like this,new power-stations,Hydro station,solar energy,other alternative energy sources,etc.