This isn’t true. The Sanders campaign never gave anything to Shadow or ACRONYM. From the reporting I’ve seen, Buttigeig was the largest purchaser of their services, with Biden as a distant second.
I mean, who knows, you have to be a lot more sophisticated to grok the FEC db, for example here's over a half million to AmEx from the Bernie camp, for what?
There's just so many payments and transfers to/from Senate and Presidential campaign and big donors that just go opaque as without knowing what the recipient really did with that money for every candidate that takes donations, this is a very hard problem to answer without a serious investigation by a team of journalists and lawyers.
So your argument is that there are somewhere secret payments from the Sanders campaign to ACRONYM, a related entity of PACRONYM, an anti-Sanders dark money group and their “tech” company, Shadow?
My comment was in response to someone claiming that all the campaigns in Iowa had funded both groups. There is no evidence of that.