why was u. s president wilson unsuccessful in his attempt to get senate approval foe the treaty of versailles?

The negotiations after WWI were nearly as convoluted as the strategies employed on the battle field.

The main objections that Wilson faced were

1. his feeling that Germany should not be dealt with harshly. Many of those in Britain disagreed. They wanted the reparations to cripple Germany so she could not rise again.

2. The main objection was the formation of the League of Nations. This was a real thorn in his side. He wanted the League to have enough power to enforce the treaties signed. The Senate really didn't want to see that as they felt that it would take away from the power they were guaranteed by the American Constitution.