This. In order for the others to be charged as accessories.....in NYC......there would have to be crimes already assigned to Spiderman with warrants out for his arrest, in NYC. That was never stated to be the case. The ONLY thing we are given that he can be accused of is the death of Mysterio, which occurred in London. NYC can't do squat in that scenario unless the UK files for extradition and requests his arrest in the USA. With no input on that video saying the others were involved, the UK can't request extradition of anyone else. So there's nothing to hold them on. As far as Peter goes, should that go to court, all they have is the word of a still alive Mysterio on video before he died saying Peter killed him. There's no real material evidence supporting the accusation. As for Peter being in control of the Stark tech, well, it'd be very easy for Pepper or whomever at Stark to bring records showing the rights were transferred and under Mysterio's control at that time.
That's a messy convoluted explanation and they wouldn't want to address it on screen, but the reality is, it would never have gone to trial in the first place.