I agree with you that all altcoin will be exchanged through bitcoin, so each time we see a bit of currency rising first, the other altcoin will rise again, because the new money will first enter by bitcoin. It is for this reason that we have an advantage in patiently holding bitcoin.
Yes its normal thing happen in cryptocurrency becauss bitcoin is the strongest one. This thing mostly happen but not all of altcoin follow bitcoin but there are other not going through the same move. When bitcoin down, other people try to get another option and it make the choosen currency has not the same move with bitcoin.