Less experienced writers/players will start in familiar places, and use the rules and techniques they understand to discover within that place.
More experienced players and writers sit with their instrument and will generally not be thinking specifically about a key to start in; their more likely to feel their way into a space which suits them there and then. It may be that the chord or thing you start on isn't the start of the thing you're writing; it's something from maybe halfway through, so you feel your way back to before it to find the story up to the first chord you played.
The observation said above about the actual instrument are important as well. A less experienced keyboardist might, for example, start with a lovely Ab major 7, followed by an Fm6, and have the urge to resolve back to C. A more experienced keyboardist wouldn't really be thinking about forcing a resolution to the sequence, they might rather be looking for ways to extend and keep the sequence moving in a circle, or pentagon, or whatever, in their mind feeling the song in Bb but never explicitly going there (as part of their internal 'gaming' of music which helps them write).
And then there are the other times when you know you have to write in a certain key because that's "what's expected". Blues in A because that's how guitarists' play the blues. A lot of brass/silver band marches are in Eb or Bb because those instruments are tuned to those keys, so when you play a written C on those instruments you get a different note.
That was a ramble, but useful to understand if you didn't already. EDM has its own things which shape the resulting key; maybe a sample can't re-pitched too much without sounding awful so you're restricted to the keys you can use, maybe you got a fancy grid controller for pushing buttons in a grid to play stored chords or whatever in which the key is completely irrelevant in terms of playability; it doesn't need to be 'playable'. Or the producer wanted the kick to hit a resonant tone in the room because, why not(!?), and that note ended up being F#, so the song ended up being in F#. So many different reasons why songs end up in particular keys; some of which will have been considered and thought about, and others will have had no forethought or planning and just end up being the keys they are!
TLDR;
People's skills, instrument choices and necessary restrictions.What factors influence an artist’s or composer’s choice of key?