Why do you think its insane to model realistic looking explosions? It's done all the time. Even if it started as a practical prop it was certainly doctored to all hell. Stone statues don't squish and guitars don't actually explode...
If you look through it you can see the top of the guitar is even cut off at the neck, either as a prop or digitally.
CGI modeling of a shattering string instrument that looks realistic would be an insane amount of work, and insanely expensive.
This was definitely mostly practical. The squished emoji ball at the end might have been CGI, but not most of this.