roots havn't set in yet, so either the water in the hole is stagnant or it isn't getting enough water. I can see the soil is a bit compacted and with clay, so add some heavy mulch or compost around that and it will help break up the soil and allow the roots to attach. It's very hard to kill a pineapple, so don't worry too much.
Next time take a stake and just press down to the depth of the core and pull the stick back and forth until you get just the right size, it will give the hole a tight fit and the soil will recompact well around that core, that will prevent rotting water in the hole, and also the hole from drying out.
