I have been growing pineapples in my backyard for around five years and this is the first time I have seen this plant grow from underneath a pineapple plant. The pineapple plant is from the top of a pineapple. Now the leaves are thin and soft and easily pliable.
If this is coming from the base of the pineapple plant it is likely just a sucker; this is the way that pineapples reproduce vegetatively. The mother plant reaches a state of maturity, usually by producing a thick stem with a pineapple on top. Then its work is done, so the mother plant produces suckers at the base and possibly slips underneath the ripening fruit. Separate the suckers and slips carefully from the parent with root attached and you can quickly generate a new pineapple plant. If anything interrupts the production of fruit this shortcuts the maturity signal and the suckers start growing.