The First time the market hit $ 345bn was December 4th, BTC price was $11600,BTC dominance was 60%. Today, same market cap BTC is at $ 8200,BTC dom 40%. Adoption of Blockchain is growing. It's more about Blockchain and way less about BTC.Its Alt season!!
There is more and more altcoins, so is normal that Bitcoin domination is decreasing. You see Bitcoin itself made 10+ forks in last half year and that will only continue. All that are new altcoins and all of them take a tiny piece of Crypto marketcap. Then there are different securities that use blockchain for their ICO. That is sort of not crypto, but right now all is put in one bag. At some point someone will have to draw a line what is what. Also different premines pump marketcap of that coin. It is incomparable with fairly launched POW coin.