From August 2017 until mid November (prior to BCH's hardfork with the difficulty adjustment algorithm) there have been some occasions (notably end of August, beginning of October and mid November prior to HF) where mining BCH was 2-4x more profitable than mining BTC. See: https://bitinfocharts.com/comparison/mining_profitability-btc-bch.html#1y
You would expect that in such cases, where mining one coin compared to the other is much more profitable, all miners would switch to the more profitable coin. However, this did not happen, even when BCH was 4x more profitable, there was still hashrate on the BTC chain (see: https://bitinfocharts.com/comparison/hashrate-btc-bch.html#1y).
What could be a possible explanation for this? I am looking to hear a miner's perspective on this.
Thanks in advance!