Legion is a series that relies a great deal on supposition and therefor there are several things in the series that have questions that are not answered or are not answered thoroughly. It's apart of Legion's surrealist charm in it's quest to subjectively explore the nature of one's reality. In fact most of characters themselves hardly ask any of the right questions and even if they do, they end up following a different train of thought soon there after.
Even looking at the bigger picture, Season 2 also introduced this idea that there is an alleged "future" that relates to this particular time line, as a "Future-Syd" time travels back to change the past, as David is going to become the villain who destroys the world...Future-Syd comes with her own set of mysteries that are never directly answered.
WARNING: Season 3 Spoilers!
This whole plot line sets up the main plot for season 3, which is
about David finding a time traveler to change the past (in order to
change the future), while Division 3, Syd, AI Robotic version of
Ptonomy, Cary & Kerri, and Amahl Farouk wage war on David and his
followers so this alleged Future-David destroying the world doesn't
-- The series never get's back to the notion of "Future-Syd" in a direct
sense, as it's the past along with "time-eating" demons (yes, you
read that right) that takes center stage.
-- The series ends with the reveal that the time traveler called Switch
becomes a celestial being in which she tells Sydney that the universe
has a purpose for her and that she will have a better future, because
of what she (and David) are doing.The series then ends on a hopeful
note, but in fact there is no physical evidence to prove that the
future is better for humanity or any known character, as Syd and David
end their scene together bittersweet.
The reason that's important to trying to answer this Question, is because once the notion of time travel is introduced, it makes the audience ask, If the future is changeable or if there is a predetermined element at play?? Are things happening for a reason or none at all???
In the season 2 episode Chapter 14, the audience is treated to an episode that shows several alternate realities in which David almost never has a happy adult life and where he becomes a danger to others. Making the audience believe that a better future might be impossible with the exception of one reality where he and Syd grow old together. It's not happy per say, because Syd has to care for a debilitated David and there is something mundane, isolating, and super tedious about it, but their love seems more genuine and less contentious than it has ever been shown on the series elsewhere.
But getting back to the tuning fork, we know before the fight David has executed a plan to get everyone and everything he needs, but it is never explained how he is able to work it all out to know what would happen, up to some point? Obviously there are things he can't predict, like Syd turning on him or getting too caught up with fighting Olivier, but yet he could set everything before that up! And in season 3, he needs another character's help
to change outcomes
with Division 3, so what happened to this ability or did Division 3
just get smarter/better technology???
Still, there is some leeway to speculate that perhaps everything happens for a reason on Legion, meaning that coincidence is not just coincidence, because of the revaluation,
of Switch (the time-traveling mutant) and her father in the final
episode, gives subtext to a "higher power" that has some greater
control or understanding of the universe(s).