I am perpetually amazed at how moronic right wing "journalists" are. ActBlue is literally built to be a common framework for individual campaign contributions to Democratic candidates. The various Democratic presidential candidates all used it as a conduit for fundraising, hence why all the top recipients are the various Dems in the presidential primary, and why Sanders recieved the most cash, because what it's showing are individual campaign contributions because all the candidates used ActBlue as a framework for online donations.
This isn't hard, the usage of ActBlue by Dem campaigns has been reported on in a wide array of media outlets.