Why did the Acts believers think the Kingdom was just over the horizon?
The Acts believers expected the Kingdom to arrive shortly because the Old Testament program placed the King's coming soon after Israel's rejection of the Messiah, with wrath and vexation first. Seeing that sequence unfolding, they viewed the Kingdom as just over the horizon, so they sold property and brought proceeds to the apostles.
Les explains that the early Acts believers were living in expectation of the Kingdom. According to the Old Testament program, not long after they rejected the Messiah would come the wrath and vexation, and then the King. Because the Kingdom was just over the horizon, they were not worried about keeping houses and lands; they knew in the Kingdom there would be no poverty and everyone would have everything. So they willingly sold property, turned it into cash, and laid it at the apostles' feet, believing the more the apostles preached the Kingdom and the more Jews believed, the faster the King would come. Les notes they did not know it would all come to nothing, which later left many in Jerusalem poor and destitute.