I'm not entirely sure what you mean.
But what I think you're asking is. Why is the sigma bond created by an sp hybrid orbital, stronger than the sigma bond of an sp3 hybrid orbital. And there are a couple of ways of thinking about why this is. A nice way is thinking about which orbital is lower in energy. And as a result, which is going to create the sigma MO that is lower in energy. Once you figure that out you can figure out which is going to be stronger (Hint the lower energy MO is going to result in a stronger bond).
If that doesn't help and additional way is thinking about which aspect of the hybrid orbitals contributes most strongly to a sigma bond. Obviously this is going to be the s. An sp orbital has much more s charcater than an sp3 orbital. So it can overlap much more efficiently with another orbital to form sigma bonds, because a greater amount of the orbital has capacity to form them.