I run a server for my country (Bulgaria) and while our neighbours Romania, Turkey have for example at least 50-100 population in one server and [TR] servers are a lot doesn't matter empty or low pop or mid pop or whatever, they have a pop at all. There are NO other servers in my country except mine but only have a max of 3 regular players that I know their names with closed eyes and another 5 players (one group) that play from time to time while waiting for Facepunch 4 to wipe at the end of the month. I am running the server x2 but still should have players even if I make it xMilion or whatever else right and people join from my country when there are no other servers? Nope, does not work like this...
While 2021 January Facepunch announced the first twitch drops and campaign in twitch and without even asking 2 streamers joined to play Rust and found my server and had 60/60 full month, also one streamer in my country used to host broken xWhatever where its vanilla but you pickup 5k rocks from the ground and they tried to turn game into RP from where they actually came (FiveM, MInecraft) with his friends that stream stream too and opened it for his viewers and he had 20 pop instantly, I had 60 cuz one girl used to stream 2h without knowing how to make anything only respawning and walking around the map but 300 people watched her... and she used to call the game new "meta" but this meta died and February again nothing... new players that used to buy game on Christmas sale or play at all abandoned it, nobody stream it in my country, only couple of players continued to play that used to play rust and from long time ago.
Apart from my story, if you have normal EU server made for everyone in Europe, not like me open for everyone but name is not targeted for the English community you should have success and not sure why player base goes down... If you had players before at least around 30-50 as you said and you combine servers so your players can gather in one server also do advertisement somewhere that server have pop and people are lazy joining when everything is ready so if they already see people inside will join too...
Btw not sure if player base is low or just a lot of new servers are opened...