Historically, the GRU has been Russia’s main agency for operating in uncontrolled spaces, which has meant civil wars and the like. In some ways, the Internet is today’s uncontrolled space.
Mark Galeotti, Institute of International Relations in Prague, as qoted in How Russia's military intelligence agency became the covert muscle in Putin's duels with the West, by Anton Troianovski and Ellen Nakashima, Washington Post, 28 December 2018
The article continues,
“What the GRU demonstrate very consistently is profound innovation with available resources,” said Joe Cheravitch, a Russia analyst with Rand Corp., a nonprofit, federally funded research institute. “That’s what really makes them dangerous.”