The British newspaper The Guardian says that European sources believe that the technicians were deployed to help prepare for a campaign of destruction in Ukraine, similar to what happened in Syria.

The newspaper quoted unidentified intelligence officers as saying that more than 50 experts, all with extensive experience in the production of explosives, had been in Russia for several weeks, working alongside senior Russian military officials.

What are barrel bombs?
Barrel bombs - raw explosives packed in containers and thrown from helicopters or bombers. Using them to bomb targets in the city means that the military using them wants to cause as much damage to the city as possible, without noticing where the explosive barrels fall.