The Alts have made tremendous gains vs Fiat. When BTC / Fiat is at its peak, don't the Alt / Fiat have to collapse? People will be selling Alts to buy BTC. Right?
This is true to a certain extent. When BTC peaks (or is on a bull run), alts tend to lose value in BTC terms. However, they don't collapse. People might think BTC is the best bet, but they will still hedge their positions with some alt coins