You can't mine "other" coins with bitcoin mining gear.
You can mine only sha256 coins.

Most of them are crap and if one big farm tries to mine it it will never cover the electricity costs.
What are you going to do with 1000 Mazacoins reward per block?
That's 0.8 $ (not even a full dollar) every 2 minutes.

The only one that counts is BCH but the reward is still 1/4 compared to BTC.
So not all miners are going to switch to BCH.