Here's a superposition of a chart of average Bitcoin transaction fees over time from July 2016 to today and a chart of Bitcoin market cap dominance.
You can see that Bitcoin's market dominance was first challenged by the emergence of smart contracts (i.e. Ethereum) which Bitcoin Core has been opposed to by extension of opposing to larger blocks. Ethereum came close to taking over market dominance in June 2017 before tapering off. Bitcoin then went on its bull run in Q4 2017 but notice that every time there's high transaction fees there's a large drop in Bitcoin's market dominance.
The largest drop in Bitcoin's market dominance came after a parabolic rise in Bitcoin transaction fees.
Just some food for thought.