I have seen more than one person point out that the dem's raison d'etre is to raise money for the DNC. Everything they do is geared towards that up to and including ensuring races remain tight. They make more sense when you view them through that lens.
I dunno how accurate it is, it certainly doesn't have to be a conscious strategy for it to be broadly applicable. When it comes to the US it's usually a pretty safe bet to assume money is the primary motivator for literally anything.