Among the altcoins in the crypto market, ETH is the Altcoin that is worth buying and investing the most, because when Bitcoin is growing fast only ETH is up and has hit the price of over $1,000. This shows that Bitcoin increases in value, ETH also increases, ETH's growth rate is faster than the rest of Altcoins, ETH is very popular and the platform is very fast.
Have you checked coinmarketcap in last few years? I can agree that Ethereum is a popular blockchain, but disagree with the rest.
How does Ethereum value increases when Bitcoin value increases? Ethereum value only corrects to Bitcoin value. Its spending power differs from Bitcoins. It has other purposes and demands.
And the speed you write - Ethereum is not among fastest blockchains. I would even say it is slow. Take a look Stellar, Eos, Tron, Doge speed (or just read
this article).
"growing fast faster than the rest of altcoins" - go to coinmarketcap, click "Cryptocurrencies" and select "Gainers & Losers", select Timeframe: 30d. You wont see Ethereum there.