This morning i received a response by the mods of why we couldnt post this steam group and get more poepl.

I believe it goes against the community itself, here is the response :

Okay, so apparently that falls under Rule 5.
They don't care if you post that you have a higher level steam group and to dm you for the link (in either self-promo or LFG or both) -
but the link isn't allowed.

There is no reason in my mind to why its not allowed but here is the rules 5 of the official discord.

5: NO ADVERTISING OR SELLING
This server is not a marketplace: do not ask for money or in-game currency, try to buy / sell / giveaway. Do not ask people to join your Discord server or COMMUNITY. No sharing cheats/hacks and where to get them or how to do them. Promotion of your channel (e.g. Twitch streams) is not allowed outside of the 📺self-promo channel.

So basicly we act as a community outside the game..