What does "strand" mean ?

Xenon02 To remain in a state being "abondened"? To be honest that sounds wierd.Like I can understand the sentence "left the lights on", left in the past and they remained like that.

I see your problem, but you are thinking only of meaning and are ignoring idiom. You can't just plug in a different word with a similar meaning and expect the result to conform to idiom. Be assured that "left them stranded" does not sound at all weird to a native speaker. Look how long it took for me to realize that you were thinking of "left" that way.

I have already mentioned "left them high and dry". Other such uses of "leave" are

left them homeless

left them tired

left them in need of a shower

The condition that they are left in is the result of whatever left them that way. Something had an effect on them, and when it ended, they were in that state—it left them in that state. The effect did literally leave, but the word "left" in this context retains very little of that literal meaning.

You are right that "left them abandoned" would sound odd, but "strand" does not mean only "abandon". The verb "to strand" derives from an unusual word for "beach", the ocean shore. You see it used in its literal sense when whales are said to strand themselves when they come out of the water and lie on a beach. It is similarly used of ships run aground, which is where the figurative sense comes from. So, you can imagine that the Yuusho were left "beached" when the empire fell, when the universe, the figurative ocean, was no longer available to them.

Xenon02 I have found many definitions about "render" in cooking .... in building ... even in programs. I don't know what did you mean throught this word

https://www.ahdictionary.com/word/search.html?q=render

tr.v. 2. To cause to become; make: The news rendered her speechless.