States had different opinions and desires on how they should govern and be governed. Some wanted to stay under the AOC others wanted Large States to have Power, some wanted Small States to have better power. Weak Central Government, Small Central Government. Who was going to pay the War Vetrans and how? One of the big deals of the Convention was paying off the army and settling the issues over territory in the Ohio Valley, subjects which had started shooting conflicts between the states before.
The states were by very much no means monolithic entities in this regard. Each state had its interest groups, which ran the individual states to greater or lesser degrees, which clashed as much with other interest groups intrastate as they did interstate.
The land question was the province of a minority -- a powerful minority, but a minority. The debt question was likewise the province of a powerful minority. They were able to push the Constitution through originally over the objections of non-members only by essentially claiming they were creating exactly what the majority wanted and then sneaking in the things they really wanted and trying to run the new government according to their own whims. They got kicked out pretty badly in 1800.
This minority isn't going to be able to pursue a policy of disunion in the interests of their own states without the Constitution. In fact, that was the whole reason they wanted a stronger central government in the first place: They had no hope competing with similar interest groups in the larger states who had no desire for inter-state conflict.
Smaller groups, like those behind the Pennamite Wars for instance, generally didn't have the individual power to push a serious policy of disunion, especially considering the Articles government (rather, the state governments themselves) seem to have been perfectly capable of solving these kinds of problems.