Steam

Nothing is "obvious" about that. What you present as the only possible conclusion from their actions is just your subjective interpretation. Could be true, of course. I highly doubt it (which is my subjective interpretation).

Someone realized that the investment required for making a PC port (or having the studio include it) is less than the money you can make from selling it on PC. Selling consoles (the hardware) isn't what makes them money, it's reasonably common for them to be sold at a loss, especially early in the life cycle. Profit comes from people buying games they take a cut from, which is unchanged if Sony is also the publisher (or even the developer).

In any case, if I'm right or wrong isn't even the point either (I'm probably wrong, too). The point is it's incredibly complicated, and nothing is even slightly "obvious" about it.