There could be several reasons followers stop following you on Twitter. Probably the most common reason is that you are not being social enough and by that I mean you are not treating people the way they want to be treated. Being social means interacting with others, not just lecturing your followers or sending out your random thoughts with no care for what they think. This also means it’s important to listen and learn from your followers.
Another common reason is that you’re boring. You need to come up with new things to say, not just keep repeating the same messages just using different words.