Why Do People Follow Jesus? Because He Has The Largest Army On Earth?

Because Truth

"The principle of Atonement and the separation began at the same time.  When the 
ego was made, God placed in the mind the Call to joy.  This Call is so strong that 
the ego always dissolves at Its sound.  That is why you must choose to hear one of 
two voices within you.  One you made yourself, and that one is not of God. But the 
other is given you by God, Who asks you only to listen to it.  The Holy Spirit is 
in you in a very literal sense.  His is the voice that calls you back to where you 
were before and will be again.  It is possible even in this world to hear only 
that voice and no other.  It takes effort and great willingness to learn.  It is 
the final lesson that I [Jesus] learned, and God's Sons are as equal as learners 
as they are as sons."

A Course in Miracles,
Chapter 5, Healing and Wholeness;
Section 2, "The Voice For God" (3pdf)
https://tinyurl.com/A-Course-In-Miracles-pdf

So even if you're Moses, or Sauron, you still have a guiding light?

"Moses said to God, “Indeed, when I come to the children of Israel and say to 
them, ‘The God of your fathers has sent me to you,’ and they say to me, ‘What is 
His name?’ what shall I say to them?”

And God said to Moses, “I AM WHO I AM.”  And He said, “Thus you shall say to the 
children of Israel, ‘I AM has sent me to you.’”

- Exodus 3:13-14