https://www.wikipedia.org/wiki/Legitimacy_(political)
This is a big part of the russian narrative about their modern warfare agenda against the mercantile empire. As they use this term all the time it's important to master it better than them in all aspect. Which is easy.
First a vs: ksa vs syria. Why is ksa more legitimate than syria?
Because of the tribe! Ksa is like the american natives, saud are the biggest tribe. Assad on the other hand is the son of a military take over pushed by shia/sects groups in the oldest war.
Now that basic application has been made let's see the legitimacy of the mercantile empire:
You want. You pay. You get.
But you can only want what the other want to sell, independantly of price, in an honnest, multitransactional way, meaning you don't guck the other once, but achieve long term sustainable multi dimensional win win aka the heavenly mandate!
Informed, free flow of data and interpretation, consent, propriety etc.
And when the ibdividualistic idealistic merchants pulled their effort to win independance and then defeat everything they did, while negociating. When the ennemies of the mercantile empire realised how paranoiacal the speculation kingdom was they folded or joined in admiration, soo much imagination in motion...
Dream big, make it bigger, and liquidate it even faster;).