Yes i am totally agree with you that you stated above. The thing more often happen when bitcoin go up and it might control the other coins prices and there trading volume as well. Yes i am also the witness of 2017 bull run we won't be surprised if we seen another bull run.
Altcoins always pump when bitcoin price rises, converse is also true in this case, if the price of bitcoin fall then altcoins also follow bitcoin price. In the 2017 bull run also, the altcoins were pumped after the bitcoin price pumped a lot, altcoins take more time to pump and they only pump if the bullish signal is confirmed in the bitcoin market, then people start to pump the altcoins too. I have never seen the altcoin market to pump without a change in bitcoin price, but it will be good to see such scenario in the future.
The price of Bitcoin will usually decide this whole market and Altcoin in the recent 2 weeks are recovering very well and many coins have reached the new ATH in a very short time. I agree that altcoins are being pumped for the time being but only the top altcoins can raise prices. During this time, consider carefully and take some time to analyze the Bitcoin price before investing in altcoins.