In a nutshell, Dishonored 2 sold "worse" than it's original - despite positive critical reception. With PS4/X1/PC combined, Dishonored 2 only sold 2.5 Million copies, while the original sold that much on PC alone. Bethesda and Arkane decided to shelve the franchise for now.
Honestly, I can't blame them. With sales figures like that, I'm sure it barely covered production costs. Great franchise, no doubt - but just as was the case with Mankind Divided, the appetite for Stealth games just...isnt there. At least not on a blockbuster level. I feel your pain though fans - the same thing happened to Dead Space.