Do you think they stopped their signature campaign because they do not have the funds to run it ?
I doubt this may be the reason because Bitget is one of those exchanges that is very much active and they get enough money in the form of fees (and that is just one source) to have a marketing budget too.
I cannot speculate why they stopped their signature campaign, and it isn't even right to do so. However, i am certain it was not due to lack of funds, they are a big exchange as far as i know, probably they didn't see results, or they don't want to spend money advertising that way, so they chose a different route.
But as you said, they opted for a free advertisement (in way of shilling) which is never going to help them in a positive way.
It is not totally free, i am sure the shillers get paid. But maybe in worthless tokens or a very little amount of money, which costs the exchange little or nothing.