I think that the main reasons, which cause especially many just set-up businesses to fail are:
1.They do not have a good activity plan and a good business plan is also missing. Or there can be a good business plan,but a good activity plan is missing. At the beginning their business will do well, but in some time the missing of a good activity plan can cause destructive damages.
2.Young business leaders do not have a good overview of their power. They can work fine at the beginning, but sooner or later their nerves just can't stand such a tension and sometime they finnish their business action because of that.
3.Young managers can't see the future and usually they will not make any investments, which will make the future investments possible. So if there will be a break-through in the technique used to do produce that good or service, they will not have necessary money to buy that.
4.The people, who start the business do not always have the necesary skills in the field of management. Some of them will learn them in action, but a great deal, especially young people, can't manage the management and fail. Of course state helps the people who has just set up a business of their own but sometimes it is not enough. They will probably have problems with taxes, because they do not know how and how much they must pay them. When they are clever enough they can solve the problem by taking an accountant.
5.Even if the business has an accountant sometimes the manager just can't handle the simple management. For example they try to order everybody to act nice and so on. All of that must be the accountant's job, manager must only be concerned of the final output, when it is good, there is no need to overmanage.
Of course there are many other things, which cause businesses to fail, for example some changings in the market etc, but they are general problems for all of the businesses, not only for those, who just started.