What do literary critics do when they make interpretations?

They interpret whatever's on the page. like sometimes they see subtext or something between the lines that the author may or may not have intended, or they take an event or confrontation and interpret it as the character/subject doing a certain thing. like they can see subtext suggesting that maybe two characters have a budding romance, or that a character crashed the car because they were intending to kill the passengers (excuse the weird example.) it's usually just when it isn't explicitly spelled out. sometimes it is explicitly spelled out and the critic can't see it for what it is. just. yeah. you get the picture