Originally, these scriptures were seen as applying to their present times. But, as things deteriorated in Israel after David and Solomon, and with the captivity, it became clear to those who viewed themselves as the righteous and faithful that as long as God allowed hostile governments and the unrighteous Israelites among them to thrive, human government was not going to bring about a righteous kingdom. So, they began to look forward to a time when God would subjugate the nations and the wicked, and YHWH Himself would set up a government in the land and rule from Jerusalem. Although God had his domain in heaven--in the clouds--it was not expected that the faithful would be removed to there. After all, there was the promise to Abraham and his seed that they would possess the land. So when Jesus taught his disciples to pray, "Make your kingdom come; your will be done on earth as it is in heaven," the hope was for the kingdom of God to extend to earth. Therefore, all these groups are the same because the kingdom possessed by the saints would be on earth.
In the passage of Matthew, Jesus is instructing and encouraging his disciples--those who accepted he was sent by God. It was part of the "good news"--those who sacrificed comforts and pleasures, and were oppressed in this age would be compensated in the age to come. Besides, all the groups would be the same because, in the teachings of Jesus, there were only good trees and bad trees--someone could not "hunger and thirst for righteousness" and at the same time be cruel, unforgiving, and oppressive.
Interestingly, in this coming kingdom, it appears that people would live long, healthy, active lives, but would eventually die. So the resurrection of the dead would have to occur sometime later. This appears to be the basis for Millennial kingdom doctrine.