I think the only way a particular clone wins out as one of the several possibly successful ones is by some combination of marketing (by which I mean, winning over "D&D influencers") and just being that "good" (whatever that means). Fulfilling a particular niche is probably also important, in a divided market, particularly if it is one underserved by baseline D&D (both because some people will still want to play actual D&D and because clones will on the whole replicate the original). I also think there will be groupings of inter-compatible clones, either around a direct 5e core rules copy or some sort of modified one (I think a version that was simplified, but then had almost everything removed and more as modular options would probably have some legs). If anything actually challenges official D&D it will probably be some group of intercompatible products that are also semi-compatible with official D&D.
I think there are additional points to be won by being free, being well supported by a reliable and google optimized website and, ideally, phone app, having excellent art, and, if it comes to market the next few months, taking some stance deemed particularly virtuous in terms of an open license.
And I think the battle will actually be won or lost around 2024-2025 or later, not based on who rushes to market this year, or who has already made it to market. The people who are such 5e fans that they want a 5e clone are mostly not in a "I shall play no more 5e forever" book burning mood no matter how unhappy they are with WotC, they'll just keep playing with their existing 5e books for the near future. The battle is over what wins over the 5e fans when they are ready for a similar game that is actively supported and free of the WotC brand.
Personally my current project is to make a low-to-no magic 5e clone, with some racial options but humans only as the default. I think that roughly covers a vast swath of literary and film fantasy settings that D&D has never suited, and at the same time it involves creating vastly fewer spells, races, and monsters and hence is more achievable.