Assuming a market is winner-take-all is a self-catalysing trap.

If any of the competitors in the market is assuming it's a winner-take-all market, then everyone else must, too.

Because if it is a winner-take-all market, then anyone who doesn't play to win will be knocked out of the game.

It might very well turn out to not be a winner take all game, but it's safer to play like it is, just in case.

Everyone playing like it's a winner take all game (e.g. deploying significant capital to get usage) makes it so anyone who doesn't play that way can't compete.

So everyone believing it's a winner take all game effectively makes it behave like it is one.