A weak launch is nothing to celebrate and rest easy over, especially when their competitor has hundreds of millions of more dollars to burn before they call it quits.
I have no interest in Stadia, but they have said many times that this is the infantile stages of streaming, that ISPs need to solve data issues over time, etc.
Google is still going to pursue this for years to come, so why would Sony and MS have "lost their fear" when Stadia has barely entered the market? No major company would let their guard down like that.
I think it's that they can see Google's trajectory out in the open now. They didn't jump into the market and make waves, so they can prepare for and anticipate the iterative improvements Google will make from where the service is now.