This is based on personal observation and studies of the altcoin market of a period of 2017/22
Altcoins are said to be the alternative cryptocurrency aside from Bitcoin and many of the altcoins are decentralized and also centralized, unlike Bitcoin which is highly decentralized and out of the control of anyone be it the developer or government Bitcoin has a total circulating supply. But Altcoin is developed by individuals e.g Vitalik Buterin Ethereum developer and teams members who are known in the society and the source codes of the coin can easily be updated which have made them not to have a static circulating which is has been the major reason why the altcoin market is hard to speculate because it circulating supply can easily be tempered more coin being minted at will which will render speculators analysis inaccurate in most cases.
First of all, btc was created by humans too (person or people) just because they are anonymous does not erase that fact. btc is completely decentralized but a good portion is in the hands of whales who can also influence the price in some ways.
Alts are mostly pegged to btc and whatever is happening with btc price will also affects price of alts, and don't forget unlike btc with multiple use case, most alts don't have utility, thus, speculating about the price of alts depends on how btc perform.