An attempt to organize a team tournament between countries!

With all due respect, why should the organizer invite each star personally?!

First of all, FTS is not "each star," but rather the best player of 2017. A player of this caliber is a rare gem, and there are good reasons to treat him specially.
Secondly, arguments for why the organizer should invite each star personally can also be found with some minimal effort.

But the real issue lies elsewhere. I think that, due to a combination of factors, Ivan simply wasn't invited in time. Armag didn't get around to it because he was already busy gathering players from all over the world and helping to captain several teams. And perhaps a few other stars, whom he had spoken with, may have dampened his enthusiasm regarding communication with top-tier players. For Armag, as an organizer, the main goal was to gather smaller teams so that the tournament would take place, while such "heavyweights" as Russia, Belarus, and Ukraine would somehow manage to assemble themselves. Well, Russia assembled itself in such a way that they forgot to invite FTS. Bishop also didn't get around to it.
There was no conspiracy here. And hopefully everything will resolve itself now if Ivan isn't put off by the rules and expresses a desire to play.
After all, there are no restrictions on the number of players or the timing of when they join the tournament.