Mindshare and hype tend to be self reinforcing and create their own gravity. BTC has the largest market share because it has the largest market share. The moment it got derivatives and ETFs listed and traded on major US exchanges (e.g. CME futures), it became the clear winner because if you are a hedge fund and want to get on the crypto bandwagon, it's easily accessible, liquid and doesn't require extra paperwork. So you trade that instead of going on some unregulated exchange where you might end up as a news headline of "Hedge Fund loses money in crypto exchange exit scam".