to be fair though;
back in 2013 (when cataclysm had been released for roughly 2 years) we had 4 different realms. instant 85, x1, x7 (im not sure) and x12. each of the servers had a population of about 1200 to 2000. aside from the x1 server which had around 200-300 if im not mistaken. could be higher, definitely not lower.
with each year molten (now warmane) started neglecting cata more and more. causing more and more people to leave.
molten/warmane kept saying things along the lines of "we have other servers to attend to", "other things have higher priority at the moment" or flat out saying that they don't really care about cataclysm anymore because the population is too low or... whatever. mind you this was before Mists of Panderia or Burning Crusade was even released on this server. when they released MOP, that started to become their excuse to not keep an eye on Cata. when TBC was released, that became their excuse to not keep an eye on cata. causing, again, more and more people to leave.
every now and then I saw a warmane gm, mod or whatever commenting that Cata just isn't what people want to play; they'd much rather play Lich King or MOP, and thats why their population was decreasing. But if your cata server population goes down 2k every year, while other cata servers keep gaining more players. it's most definitely not the case.
so now, in 2018. with those remaining 150 people. considering Warmane itself has done barely anything to Gain cataclysmic population. they were the ones keeping the cataclysm side of the server running.
to some people, cataclysm is the only form of WoW that they play. Warmane = cataclysm for them. if warmane removes cataclysm from their servers. to them. warmane has died out.