The reason why they went out of business was mainly due to not having a decentralized version of doing it. I remember one telegram group for pump and dumps that literally picked which coin will be pumped and dumped by just the last digit of a litecoin chain and that was actually not a bad idea, nobody would be able to get in early and everyone had equal chances. Now pump and dump is not similar to signal groups I know but there was similar reasons why they got burned out as well.

Signal groups were the same, some people got it early and bought, others got in too late and burned out, which resulted with only few people making a profit and most of the people losing money. Also most of the calculations were based on charts and we all know charts were not a good indicator most of the time.