Interviews with the victim, the witnessess, and the perpetrator(s) could require weeks to complete.

It may be a tough case to prove. I hope there is cell phone video. However, due to the apparent short timespan of the altercation, it is unlikely that a video of the critical moments was recorded.

Or will the Cemetery staff let it go?

I would think there might be witnesses.
But even if the case cannot be proven, at least charges could be filed.

Of course, I detest Trump and his cringe-inducing associates. They were passive-aggressive, to say the least, in the entire episode. They never asked permission from the cemetery personnel regarding their abominable trek across the hallowed ground. I would like to see the Team Trump player who pushed the government employee to spend time in jail. After the despicable actions of Trump and his aides, a repugnant Trump spokesman suggested that the victim had not identified himself as holding a position of authority regarding the cemetery, which is likely a lie. That same spokesman also said that Trump's team is in possession of videos of the scuffle, which also is likely a lie. Anyway, police are loath to file charges unless the evidence tends to show that a conviction will be likely.

I hate to see these people get away with their despicable deeds.
But it may be not a viable court case as you say.

It was one of the many poison pills he left for President Biden and the mainstream press has given Trump yet another pass. Now that he's running for reelection, he thinks it would be a good photo op to commemorate the chaos, and bloodshed he originally set up to happen. Could Trump be any more sick and twisted?

Donald Trump's appearance at Arlington National Cemetery this week was already controversial. Then the public learned about an "incident."

Link to tweet