As the quality of forum members' posts keeps improving, advertisers are getting more interested in promoting their brands and feel comfortable upping their budgets. We know that higher payouts attract the best posters, which is why we should value the quality of our posts... I can only speculate that this is the case.
I wouldn't say the reason is what I put it in bold. The quality of some posters might be improving but I don't think that's the main thing. The main thing for me is that we are in a sort of bull market for bitcoin, we have had a dip recently that has started to recover but clearly we are not in a bear market like when the price is down 85% from the ath. And it seems that the best of the year is yet to come, so it makes sense for companies to invest in advertising.
Don Pedro Dinero is more correct about this. I do not think that the quality of the posters in the forum has significantly improved. There might be improvement but not a clear improvement. I have read how the forum has lost some quality posters in the past and I have also seen that the forum hardly gets immediate replacement. The more populus the forum becomes, the more we have shit posters flooding the forum.
So, we should not attribute the influx of new campaigns to quality post of the forum, but to what Don said above, it is because we are in the bull run market.
We should also not forget the individual efforts of the signature campaign managers. Take Little Mouse for instance, how many projects he convinced to promote in the forum.