The point of split-pushing is to establish an ultimatum. You want the enemy team to have to choose between the split-pusher and the other 4 grouped team members so that if they go for one, the other will be able to push and/or take objectives. However, for this to work, you and your teammates need to coordinate a situation where you are actually split AT THE SAME TIME. For example, if you start split-pushing and for whatever reason the rest of your team isn't grouped, the enemy team can easily pick you off then head for an objective or the rest of your team with no pressure on them whatsoever. This is NOT your team's fault, it falls upon the split-pusher to make the decision of whether he should begin his job or not. Hope this helps!