this is really so easy? why wouldn't miners do this. and what happens afterwards? what will the devs do after the hard fork?
The founding devs would most probably stop working on zcash, but there would be new ones queuing up to do a takeover. The ethereum devs were greedy, but 20% is so greedy that zcash probably won't have much of a future if it isn't changed.
I first heard zcash has a new fangled alternative to POW and POS that was touted as assisting decentralization. If GPU mining it through pools has given one pool over 51% of the mining power the new algo hasn't helped decentralization at all.