DD
Your point is well taken. We know that many did turn away with disappointment when Christ died. Many had expected him to rule as an earthly king with Jerusalem established as his capitol city. But the gospel message continued on with the inclusion of "Christ crucified" and gave significance to points that Christ made during his ministry. Example: "My kingdom is not of this world...." Christ said that many things not understood would be revealed later. But the basic "good news of the kingdom" remained the same. And this simple message drew in the multitudes as it spread throughout the Roman empire and beyond.
I think, though, that the Watchtower has gone well beyond the misunderstanding of the early Christians. It is promoted its own teachings that negate the scriptures. For example, the teaching of a invisible presence of Christ is exactly what Jesus' warned his followers about: "At that time if anyone says to you 'Look, here is the Christ' or 'there he is' do not believe it. For false Christs and false prophets will appear.....So, if anyone tells you, 'There he is, out in the desert' do not go out; or 'Here he is, in the inner rooms' do not believe it.' "
It is interesting that the Watchtower's teachings of these subjects evolved out the disappointment of its expectations and interpretations. It had to justify its own self appointed position as God's spokesman. And as in the case of the early church, the leaders were primarily responsible for the errors that crept in.