Think about it like breaking a cookie. It will break slightly differently each time you break it, and produces two major pieces (not necessarily equally sized), and some crumbs. While it is easy to break a cookie, exactly how it will break will be determined by lots of variables, so many, that measuring the statistical frequency is usually how outcomes are predicted. Some reactions require certain minimum energy thresholds to be overcome, and the energy of an incoming particle can determine how likely certain types of decay are. That being said, a neutron is actually absorbed by the 235, which becomes unstable and breaks apart. U-235 fission produces an average of 2.41 neutrons per fission, the neutrons being analogous with a seed or something in a cookie that cannot break apart easily, and so either is in one half or the other, or in neither as a crumb.