My impression of the post-street fight charges were that at one level- Behan and the county Democratic Party- The charges were a political opportunity to hammer two of the strongest Republican contenders for the upcoming Sheriff's election: Virgil Earp and Wyatt Earp. The fact that it took Ike Clanton to file those charges while the prominent attorneys who were county Democrat politicians did not speaks volumes: In criminal prosecutions with political repercussions, the axe has two blades and will cut just as catastrophically if it falls back on the one taking the chop with it as it will if it cuts what he's aiming at. In short, they dared not swing and miss. Since the county Democrat attorneys didn't file the charges, it pretty much indicates that they were afraid such charges wouldn't stick- Swing and they were afraid they would miss.
Ike Clanton's motivations and judgment on when and why to file the charges were a whole different matter. Primarily, and most understandably, he'd watched his younger brother and two good friends shot to death. Anybody in such a position would go through the normal human stages of grief, including anger. In Ike's case, anger apparently manifested itself as a determination to see the Earps and Holliday dead for the deed. He wisely and correctly started with The Law.
Unfortunately for Ike Clanton as well as many other persons who live through similar losses, not every violent death is without legal justification, and the only way such justification is established is through the courts. Ike gave it a shot, forced the county's hand by filing charges himself as the law then allowed, and it didn't work out as he wanted it to- A swing and a miss.
The thing is also that, by his filing as he did and when he did, he forced the county to prepare and pursue a criminal presentment Right Now when holding off and letting the county investigate it and get their ducks in a row then file when they had good witness testimony and firm evidence lined up (if they could ever have done so) might have resulted in a different outcome. As soon as charges are filed, the Speedy Trial rights of the accused kick in, and if the charges are thrown out by the judge at the preliminary hearing AND the Grand jury (as these were) then the defendants are generally protected from facing the identical charges ever again- The government gets one bite at the apple in criminal prosecutions, a very fair and sound doctrine that keeps the government diligent and honest. If they could continually refile the same charges over and over until they get the outcome they want, the opportunities for abuse and oppression are endless, which is why fundamental American law blocks them from doing so. Ike forced them to take their one and only one bite of the apple right away, and when it failed it was over for all time.
Ike's hatred and impatience slammed the door on what he wanted, which was to see the Earps and Holliday hang for killing his brother and his friends. This is why the law needs to be applied and crimes prosecuted dispassionately and prudently- Hastiness and vindictiveness lead to failure and abuse far more often than they lead to any scrap of justice. Not saying that waiting for the government to get around to filing their best prepared case would have worked out any better for Ike than it did, but Ike's actions GUARANTEED that the government couldn't take their time and present their best case.