The ending of 'Once Upon A Time... In Hollywood' was always going to be something particularly tricky to navigate, precisely because the fate of Sharon Tate was so truly horrific that putting it up on screen would be exploitative.
So, what does Quentin Tarantino do instead? Well, he writes his own version of how it would have went down if he - or rather, his characters - happened to be in the scene. It's not surprising that Tarantino visits gratuitous and - dare it be said - satisfying violence down on top of Manson's followers, Tex Watson, Susan Atkins, and Patricia Krenwinkel.
It's almost comically violent, with Leonardo DiCaprio's character torching one of them with his flamethrower that he just so happened to keep next to his pool. In a similar way, 'Inglorious Basterds' ends with a history-correcting end as we saw Hitler shot to shit by two American paratroopers - one of whom is Jewish - and then blown up by Shosanna Dreyfuss, herself a French Jew.
Throughout the movie, what's clear is that Tarantino not only loves the era, but is clearly viewing it from the perspective of one who never experienced it. It's all glorified, bathed in yellows and gold, music coming through perfectly clear and everyone smiling as they attend party after party. The only sense of darkness we get is when Pitt's character goes out to the Spahn ranch, and has that odd moment with George Spahn and tries to understand the situation.
It's probably as close as the movie was going to get to reality, as it's well-documented that the real-life Spahn was seemingly fine with Manson's followers living on his land in exchange for sexual favours.
Yet, for all of this, so much of 'Once Upon A Time... In Hollywood' is wrapped up in fantasy. The movie and TV industry, though it treats Rick Dalton and Cliff Booth harshly, is beatified. It never once delves into any of the very real problems of the era because, well, why bother? It's Tarantino's fantasy world, as idealised and perfect as he wants it to be.
The ending is just another part of that. In his eyes, the Tate-LaBianca would-be murderers are getting exactly what they deserved and that the story ends with a sleepy Sharon Tate introduced to Rick Dalton by Jay Sebring. It's no surprise that Tate's sister was supportive of the movie, despite being initially reticent.
Throughout 'Once Upon A Time...', we continuously see Sharon Tate as a happy, carefree woman who's enjoying the life and times of a rising star in Hollywood. That her death was so violent, so senseless and so tragic only compounded this. As much as she was the cipher for the glory days of late '60s Hollywood, her survival is Tarantino's fantasy living on.
We know it didn't end that way, but it doesn't matter because it's a fantasy. It's as much Tarantino acknowledging his own fantasy of '60s Hollywood as anything else.