Tether may be involved, but it is big Tether-owners that do the manipulating. IMO, they control many crypto prices. Mostly I think they pump up the ones they want higher and make sure BTC is always on top so it seems to be a legitimate Bitcoin.

Probably everything is manipulated, or at least Tether has a (direct or indirect) effect on everything in this market.

The difference lies here: BTC maximalists will tell you that Tether is honest because if it goes down, their investment goes down (even if it’s propped up by a scam).

BCH supporters will tell you to let it crash so that honest price discovery can happen again. Even if that means going down for a time.

If it can be destroyed by the truth, it deserves to be destroyed by the truth.

Because affiliated businesses (Bitfinex, Blockstream, FTX, Celsius, Binance, others) that hold btc as collateral against tether given to them are protecting their interests. Alex Mashinsky of Celsius has stated that if btc price dropped, they were required to purchase more btc to rebalance. This would be like a bank expecting property owners to purchase more property if prices dipped and the bank even lending you more to do so. Artificially creating demand did not end well in 2008 with subprime mortgage crisis.

EDIT: Big exchanges have close relationships with tether, which facilitates liquidation of shorts/longs and front running. Any exchange needing liquidity has easy access to tether if they ‘co-operate’.