You got flagged because Bitconnect is most probably a ponzi scheme.

I'm not sure about the exact details because I didn't care, but i heard rumours that the trading bot which supposed to generate the profit for investors actually doesn't exist.

If that's true than the only thing keeping it alive still, is the inflow of new users and their money. Lots of people will lose lots of money.

[Many Steemit users] believes: promoting a scam is the same as being a scammer. So they doesn't want Bitconnect to be advertised on Steemit. And will flag everyone who tries to post anything positive about it.