Was it air defense, or the struck base itself, like not having taken dispersal measures etc.?
Since it was a classified military trial, information is limited. However most news sources seemed to suggest they were in charge of "air defence".
This news report says:
The prosecutor's office considered that the enemy's "surprise attack" became possible due to insufficient air defense coverage of the airspace in the border zone.
This report also suggests the same:
According to the investigation cited by Kommersant, in the spring of 2022, the officer did not organize sufficient cover with air defense systems, and as a result of a strike by the Ukrainian army on the Belgorod region, seven soldiers were killed.
This news source suggests there was deficiency of both defence and offence by the officers:
Their alleged incapacity to prevent the shelling of a part of the Armed Forces of Ukraine, including an ammunition depot in the Belgorod region, led to the death of seven servicemen and the destruction of 15 pieces of military equipment.
... Subsequently, as part of the investigation, the commander of the unit, Lieutenant Colonel Bondarev, was also included in the list of defendants, who, it seems, failed to provide adequate protection for his unit, including protection from rocket and artillery attacks.
And are there any similar cases ongoing in Russia?
This news report says this was the first trial of this kind, under this law:
The First of its Kind
This conviction marks the first time Russian officers have been sentenced under Article 340 of the Russian Criminal Code for failing to repel a surprise attack ...
Precedent Set; More to Follow?
While this is the first conviction of its kind, it may not be the last. According to Russian news outlet Kommersant, every missile or drone from Ukraine that goes unchallenged initiates a terrorism case. If they are not intercepted, a negligence case is opened against the responsible officers. The sentencing of Bondarev and Dmitrakov could be the beginning of a series of similar convictions.
... The officers were held responsible for failing to prevent the strike, a charge that has now been legally upheld. Their conviction serves as a stark reminder of the human cost of war and the responsibilities placed on those tasked with preventing such incidents.
Though the charges of "terrorism" sounds like an overkill to me, apparently it's not unique to the Russian military. The US military also has similar equivalent laws - Dereliction of duty - that even prescribes the death sentence during wartime:
Punishment can include sanctions up to and including the death penalty (in times of war). Outside of wartime, the maximum punishment allowed is a dishonorable discharge, forfeiture of all pay and allowances, and confinement for 1 year (10 years for service members receiving special pay under 37 USC 310).
(Most news sources seem to be citing the Kommersant report that you have also referred to in your question. I didn't find any western news sources reporting on this incident, yet.)