Since most of the major altcoins move up or down at the same time as bitcoin, aren't they all controlled? How does it work?
yep. its called arbitraging
where people dont just day trade left and right between btc<>usd
but instead play the wider markets
usd>btc>eth>usd>btc
usd
what you notice is
each market/community(coin) should have its own 'price discovery' of its own community/utility/desires/speculations/benefits
however if the community is weak/low/uninterested. their own market 'price discovery' efforts do not move much. meaning it allows other coins arbitraging effort to affect the altcoin market more than the altcoins own price discovery efforts can defend against other coins arbitrage
bitcoin is strong so yes bitcoin over powers weak altcoins. when bitcoiners arbitrage between the markets
.. here is the thing.
ethereum has locked up most funds into "stake" meaning their community is passive rewarding itself new coins. but not then able to trade those coins on the market.. thus has become less price discovery independent due to their weak market. their stake is locked until they release code to allow stake unlocking (so people can actually spend their passive rewards)
this means ethreums price speculation is controlled by bitcoin. and is being artificially held up by bitcoiners
but wait until those who staked can unstake. then there will be a wave of people selling coins on eth and breaking the shadow tracing arbitrage of bitcoin .
here is another thing
when ethereum switched to pos. the underlying cost of creating new coin dropped by 95% meaning there should have been a correction of price discover by a 20x drop/correction
however due to the lack of 'unstaking' the arbitraging of markets. that correction has been delayed
but as soon as unstaking is allowed and people can then sell their eth where lots of eth suddenly hits the market. expect the 20x correction
the eth-btc ratio will change from 14:1 to 280:1
meaning instead of ~$1.6k eth it will be ~$80
eths underlying price discovery of cost of coin reward is about $40 a coin.. down from 800 a coin
so right now eth is artificially marketed at a 40x of value
which pre pos it was price discovering at only/ever a speculation of ~1.5x-6x
thus yes eth is going to correct