It depends on what the prosecution can prove beyond reasonable doubt to a jury of one's peers.

The Santa Fe District Attorney believes they have enough evidence to prove the charges. This has taken a long time so they must be pretty sure of a conviction.

As to stuntmen being charged for crashes, a quick web search shows there are several times where multiple people were charged in fatal accidents- both those directly involved and the producers for "allowing" the accidents to take place.

Not all were convicted but there is legal precedent.