The third trailer for Inception was one of the most influential trailers of the past 10 years. If you don't remember, it's stand out feature was its enormous BRAAAAAAAM sound.
The iconic sound was created via a collaboration between composers Mike Zarin, Zack Hempsey and trailer editor Dave Rosenthal. It evolved over the course of the first teaser, second teaser and full trailer. If you're curious, this Indiewire article details its creation, and this Hollywood Reporter article interviews some more trailer creators about it.
After Inception's final trailer, it seemed like every single trailer used some variation on the sound. I don't know how long it took for the imitations to slow down, but it was quite a while. I doubt it'll ever go away entirely, but right now it's nowhere near as prevalent as it used to be.
Why the heck did this take off as much as it did?
I suspect it's a combination of trailer producers wanting to create something as impactful as the Inception trailer, and also high up decision makers who simply who saw the Inception trailer, then said to their producers: "Make it just like that."
As a trailer editor I try to keep abreast of trends in the industry, but I'm always very hesitant to ride the wave if that trend is something as in-your-face as the Inception BRAAAAAAAM. I've only made one trailer that used BRAAAAAAAMs, and that was only because a client specifically requested it. When I was told by my producer that's what they wanted, I just thought to myself: "...really???"
Imitation aside, why might a trailer editor want to use BRAAAAAAAMs? I think it's because it functions as both sound design and music. Every time I have to do a music search for a trailer, I tell myself that I'm looking for something different than what I've used in the past, but what I inevitably seek out is a music cue that structurally similar to previous music I've cut with, but the instrumentation is more fitting for the current project. That is to say, I look for a music cue that has a sense of rising action that periodically has big and strong beats sprinkled in.
It all comes back to the modern trailer editing structure where a line of dialogue is followed immediately by a sound effect or big beat in the music cue that punctuates the story beats. It's much easier to edit to that structure if the music literally is made for it.
The Inception BRAAAAAAAM music is basically the result of someone taking those big beat punctuations, and making the slower parts in between very easy to shorten or lengthen without interrupting the phrases of a melody, or extending it by looping something it and over. Of course, the actual Inception music was custom composed, but I think the imitators follow this composition idea. This more loosely defined music cue makes it easier to move sections of the trailer around or vary the pace.
Normally I look for lines of dialogue of a length that naturally fits in between big beats or minimizes the amount of music editing I have to do, because interrupting the phrase of a melody but cutting out of it too soon can either consciously or subconsciously leave an unresolved feeling in the audience's head.
Take a look at where the BRAAAAAAAMs are located in the final Inception trailer.
You can see that they're not placed at regular intervals. Sometimes they're very close together, and other times they have more room to breathe. Since even music composed for trailers is typically driven by some sort of melody, it's difficult to have this sort of pacing flexibility unless it's custom composed. But since BRAAAAAAAMs tread the line between music and sound design, it doesn't feel weird that their intervals vary in the piece as a whole. As long as they're consistent in each section, it feels totally fine.
Another reason a trailer editor might like BRAAAAAAAMs is that they give a starting point for the structure of the trailer. A blank timeline is a terrifying thing for an editor, just like a blank sheet of paper for a writer, or blank canvas for an artist. Anything that creates some constraints is always welcome, because it allows you to hone in on the problem.
A music cue of Inception-like BRAAAAAAAMs says to me: "Put the biggest, most epic shots here, here, and here" then figure out how to connect them. This is also what it's like working on trailers with title cards. For example, an accolades trailer with 4-5 quotes. Since I know those quotes absolutely have to go in, I'll put them in my timeline first, then work around them.
That's kind of it really. BRAAAAAAAMs are high impact, and easy to cut with. Music searches can be the most agonizing part of the making a trailer (if not THE most), so anything that restricts that search is a welcome relief. Trailer editing is never easy per se, but any editor would gladly use any element that's huge and dramatic, sets up constraints, AND allows for flexibility.