Indeed, the pressure from the entire Canadiens' environment may have been too heavy for Jo. He was supposed to be the future star, the face of the franchise.
Remember, Marc Bergevin wasn't able to sign Alexander Radulov, so he traded Mikhail Sergachev for Drouin to compensate for this loss.
However, from what we've learned, it had been a possibility for a long time. Tony Marinaro recently mentioned that Jo wanted to come to Montreal when he was with the Lightning, and he believed he could handle the pressure.
Furthermore, the fit didn't seem to work with Steve Yzerman and Jon Cooper in Tampa Bay, so a trade was inevitable.
Unfortunately, we know how it turned out. The Canadiens should have kept Sergachev, but it was worth a try. Jo really wanted to be the face of the franchise, but he was never able to fulfill that role.