Why did the angels make a point of closing the door?
Seforno: They did that in order to encourage the men of S'dom to continue searching for it, in order to demonstrate the extent
of their evil.
That even in their blindness, they did not desist from carrying out their original intentions. Refer to 19:11:1:1.
Bear in mind that the Din of S'dom was not yet complete and that the enfolding scenario was part of its judgment (Refer to 18:26:1:1)