Say what you want about the Chinese economy, but when it sneezes, the world catches a cold. The past two years, China has been deleveraging and that has resulted in slower growth from Germany to Australia. China's manufacturing PMI is shown in the chart:
We can see that in March, the PMIs turned positive again after 3 months of contraction. The market is taking this as a sign that the worst is over and that the stimulus has kicked in. If PMI readings are in-line with expectations, or even better, a beat, then that's going to set up positive vibes till the next crisis.
While i'm not a fan of soft data like PMIs, they're just a bunch of surveys after all, there has also been an increase in electricity output and lending. There's reason to be optimistic!