Why has the Petroff Defence become more popular? In the last few years, the Petroff defense had almost disappeared from the super-grandmaster scene with Top players preferring to play the Berlin. However, in this year itself, the Petroff has seen some sort of a renaissance with Fabiano Caruana in particular playing it 4 times in the Candidates tournament itself. Top players like Nakamura have also played it a few times recently(particularly the US Championship) 

My question is, Why is the Petroff being played more recently? Has there been any novelty that has been uncovered and everyone's just analyzing it more and more?
Possibly it's the evasion of the evasion of the evasion.

GMs evade the Ruy mainlines by playing the Berlin, then they evade the Berlin by playing the Italian and now they might just start to evade the Italian by playing the Petroff. 

My hope is that they'll evade the Petroff by playing the King's Gambit.