This is revisionist history.
No, it's how it went down. The disorganized v. the organized. In the time it took for any organization to come about, damage was already being done.
The 'all lives matter' nonsense began basically instantly after the phrase 'black lives matter' was coined. It was very clearly a deliberate attempt to cloud the issue. Blaming a movement for the inevitable attempts to attack it is silliness.
The issue was clouded to begin with. The term lacks implicit context (I mean, have you seen the sky lately? It's blue...), most people are very much disconnected from the context, and are content enough with the status quo. Yet, early rhetoric was assuming everyone and their dog understood the context, resulting in BLM alienating outsiders, rather than gaining support (that in this group's mind, whites don't care about blacks; which is not how most whites see things, but has truth behind it nonetheless,
and it is a perspective that needs explaining). It was also spawned from an event that didn't turn out like it was originally portrayed, which, by that time, was somewhat expected by most, to boot. Regardless of what it was to be called, something like ALM was begging to be created.
I think it's quite fair to criticize a movement for being
too democratic, because it invariably encourages malcontents, and emotion-fueled talk without enough who will get the most attention. As a problem, it goes back to union formation, and 2nd-wave feminism, so it's not like that's a new thing. Allowing the media to have a field day with rabble rousers (like the Sanders' hijackers), and radicals (that reporter that got all in the news for being intimidated/harassed away from a demonstration for being white) only feeds opposition more, and was both predictable and preventable. None of that helps get a good point across, and makes up for many times as much positive work. A movement's message being what someone who says they're for it wants it to be is too much flexibility. It needs to be defined clearly ASAP, not assumed.