Firstly the fucking cheek, possibly years of inflammatory (often blatant bullshit) headlines could have stoked this.
Secondly, its very interesting to see the photograph they have chosen to use showing a clash between a black guy and a white guy*, further stoking the narrative that its some kind of race/culture clash.
*FWIW the picture was taken in Bristol and showed a black guy who was out with his missus being attacked.
Oh and thirdly, Johnson is the PM and thus has been in charge since day 1!