Bitcoin is #1 because of two things: trust and liquidity.
It's the most trusted because it's the oldest codebase that has worked decently well (if you can pay a high fee in some cases) for the most years.
It's the most liquid in terms of exchange adoption and high market cap. Because of this, it's actually the most efficient way of making very large transfers (which is why the Bybit hackers wanted it).
Until something else becomes more trusted or more liquid, or is overwhelmingly used and useful for other things, Bitcoin will be on top for a while.