If you're not invested in the apple ecosystem, then the Mac would have to have something that is absent in a windows machines. In the past that would be a great design, high quality, better components. Today the competition has largely caught up and for the platform agnostics, they have full freedom in choosing something that best fits their needs and budgets.
I think some (many?) people who are invested in the apple ecosystem are rethinking their brand loyalty. With apple ever increasing the prices, and the issues with the T2, the keyboard, the speaker crackle, the coil whine. it makes sense that some are reevaluating whether a nearly 3,000 dollar laptop is a good value for you money. I am happy with my laptop, and its been solid, no coil whine or T2 issues, but I'm right on the fence for any future purchases. Hopefully I'm years away from making that decision but I nearly went over to the dark side in 2018 (windows machine) before buying the 2018 MBP.
As for the Surface Pro, its not really a competitor of the macbook pro. This is coming from an old SP owner. I did get one to replace a MBP, and found it limiting at times. The MBP offers more power and better usability as a laptop. The surface pro is a nice machine, but it does have drawbacks, for instance. center of gravity is different then a laptop. Its more wobbly on your lap when typing because the keyboard is so light and all of the weight is in the display. I now view the SP as a iPad or a Macbook competitor. Something small light for nothing too intense. Just my two cents.