They aren't losing fans with PC, it's the opposite: last month they achieved the all time high monthly users for PS and PS5 became their fastest selling console ever (with around half of sales being from new users). Plus PS5 only sequels of the titles ported to PC are selling the same or better than the previous titles.How is it good business to lose fans to PC platform and Steam?
And of top of that they'll be making hundreds of millions of dollars every year in PC, where they are making new fans. And most of their PC titles are ports of old games that took them only around a couple years each to be made. So it's highly profitable for them, money that later can use to fund their super expensive AAA titles.