Why do enlightened beings want to save sentient beings? Does everyone want to be saved? Does enlightenment always comes with compassion so that all enlightened beings aspire to save sentient beings from sufferings? Or is the question 'why' only showing that I am using my discriminating mind to try to understand things?
Another part of my question is that I think most of the people  on this earth would not say they are 'suffering', there might be obstacles and negative feelings from time to time, but most people enjoy getting attached to the experience of pleasure, longing, love, etc. Most of them enjoy this worldly life so much that they wouldn't even thinking of standing back out and look at this kind of life that everyone is living from an 'outside' perspective. So my question is that why would all these sentient beings forgo this mostly pleasurable life (with net happiness larger than unhappiness, and all sorts of biological/neurological signals from their bodies guiding and incentivizing them to continue living and reproducing for the continuity and advancement of the species) to practice Buddhist teachings, to let go of things and pursue the state of nothingness? For most of them, it would be giving up net positive happiness to attain a state of nothingness and tranquility. Is that what everyone wants and needs? How do you convince them to do this? How do we save ALL sentient beings? Should we do this? Why do enlightened beings do this?
These questions have been tormenting me for some time. Would be great help if someone can help me understand them. Thank you!
If you knew of a really good restaurant, would you keep that knowledge to yourself, or would you take your friends there? If you saw a fantastic movie, would you go home and muse about it in private, or would you try to get your acquaintances to go see it? There's nothing mystical or magical here. People like to share good things with others; sharing knowledge of what's good creates value without cost. Why wouldn't one want to do it?
Now, people who lack understanding can get contracted. They worry that if they share knowledge of a good thing, it will create demand, then shortages. The thought of sharing the knowledge of something good invokes a fear of loss; the fear of losing something good invokes an urge to grasp; soon such people are trying to stockpile what's good, to decide who is worthy to acmes it and who is not, to police the boundaries of what they have determined is 'theirs' with all necessary force. The 'good' becomes like the ancient myth of the dragon's hoard: an accumulation of value for no purpose save to stave off that fundamental and abstract fear of loss and magnify the ego.
Are such people happy? Well, I suppose yes, but only in the twisted sense the they can share the knowledge of their own superiority with others: &quot;I have, and you don't&quot;; &quot;we can do this, and they can't&quot;; &quot;our people are worthy, theirs are not&quot;. Their suffering isn't 'misery' in the classic sense, but more that they have no real understanding of their own selves, Like Milton's famous passage:
And they, so perfect is their misery,
Not once perceive their foul disfigurement,
But boast themselves more comely then before
And all their friends, and native home forget
To roule with pleasure in a sensual sty. — Comus, lines 73-7

Without that comparative — without the idea that 'the good' is in short supply, and that one has beaten others to secure it for oneself — this kind of wealth has no value, and makes no one happy at all.
Enlightenment is freeing — it frees us from the enchantment of that 'hoard' mentality, and the web of cravings that surround it — but it makes one conscious of the fetters that others are subject to. It's bittersweet. But still, it's a good that anyone who finds it would like to share, if they can figure out how.