Next week, VidCon will be sunny with a chance of development deals. I’m already imagining agents lurking behind every pillar at the Anaheim Convention Center. We’re still in the throes of Backsession fever and, in a time of so much not-good news, that can look like a state of grace. But the real force behind “Backrooms” and “Obsession” isn’t YouTube-to-Hollywood. The invisible variable in every hit is compression. Under Pressure Every hit has a …