One thing I've observed is that a subset of that weird and interesting music is only possible due to the availability of musicians who have gone through the classical training. Having access to players who are capable of doing anything you ask, is what allows composers to be even more adventuresome, for two reasons. One is the sheer ability to play the stuff, and the other is the efficiency of doing it with a minimum of rehearsal.

The same has been true to some extent in the past for popular music. Up through maybe the 70s and even 80s, a lot of the instrumental parts for the "hits" were recorded by trained jazz musicians.

> Top-tier symphonies world round are doing crossover concerts with pop artists

And they have been for a long time:

https://en.wikipedia.org/wiki/Concerto_for_Group_and_Orchest...

My understanding is that many of the classical-heavy orchestra schedules are driven by donor expectations.