You're funny, the link you posted actually shows Bitcoin bleeding market share for all of 2017: https://coinmarketcap.com/charts/#dominance-percentage. This is after a 30% gain in BTC fiat value, which should drive up the BTC dominance, but has largely failed to do so.

It's very common for Segwit fanbois to engage in reality distortions. A good example of this is their attitude toward Bitcoin Cash. It's the number 3 crypto in the world, featuring a perfectly equitable distribution airdrop to the entire Bitcoin user space, 1700x lower fees than BTC, ~20x faster confirmation times, good mining support, and no troll devs who sit around bashing people on Reddit rather than writing code. Finally, it's absolutely a fact that Bitcoin Cash follows the original Satoshi vision, and Segwit/Blokstream coin does not.

Even if you don't believe Bitcoin Cash is the "one true Bitcoin", you need to start confronting the facts on the ground, unless you want to be left behind...