Because the title of the post and the image implies that JWs were pro-actively targeting the attack venue to take advantage of people's shock and grief.
The reality is that, whilst the location is close to the attack site, it's a shopping centre where Witnesses regularly set up their cart and for them to be there during the day is not unusual. Of course they would be hoping to use the tragic events to feed a conversation but there is no evidence to support any kind of assertions that the Witnesses were descending mob handed into the area to exploit the situation or similar, something that this picture has been used to try and imply in various threads I have seen here and elsewhere.
To be fair, some on the JW side of the fence have also been quick to create pro JW propaganda from the image as well.
The truth is that this is one cart in an area you would find it most days of the week and the Witnesses manning it would only have had the opportunity to evacuate from the nearest bench with their coffees and smartphones.
