Some jackass dug the term up out of the history books a few years ago and now many very online people use it as an insult against people they perceive to be evil and ruthless.

In the period from about 2012 to 2020 it was used in internecine squabbles between MLs and anarchists, with all MLs (not just those who would have supported the Moscow line on Hungary) being called tankies, and anarchists being called anarkiddies. Sometimes this was serious, sometimes it was good-natured teasing, and it depended on context. Around 2020, liberals somehow absorbed this usage from anarchists, but spread the meaning even further, to include initially anyone supporting (critically or otherwise) present or historical AES (actually existing socialist) states, then to anyone opposing US/NATO) foreign policy, then eventually to anyone to the left of Joe Biden. It got attached to brainworms US liberals had been cultivating since the "Russiagate" conspiracy theory of 2016, and accelerated with the Russian invasion of Ukraine.