It can - if it helps with the economies of scale, and makes us "get off" fossil fuels earlier.
Normal usage has already done this. New renewable energy sources are cheaper than new fossil fuel sources. Fossil fuels exist mainly today because they have already been set up but mostly for political reasons. Many political parties have built their personal brand around fossil fuels and will continue to use them even when it is illogical.
Not if you consider the intermittency/storage issues.
(And guess what - intermittency isn't a big deal for cryptomining / SETI/Folding@Home either!)