Their execution of the whole thing was all wrong.
I listened to Totalbiscuit's interview with the owner of Nexus mods and developer of one of the most popular mods for Skyrim, SMIM, and they mentioned that they were not contacted in any real capacity about how this thing should have been done.
Why would you not contact an experienced modder or the guy who has had 14 years of experience hosting a community for mods about how a paid service should be run?
On top of that, Valvethesda apparently went around and contacted a number of modders somewhat under the table and asked them to create brand new mods to serve as posterchilds for the new service, giving them 45 days to do so.
45 days isn't nearly enough time to make a mod of any significant quality, let alone one that people would actually pay for. That's why the initial selection of mods on the service was complete ass, and other modders with more developed works who elected to put up their mods (SMIM dev) for sale didn't even get a chance before Valvethesda tore the whole thing down because they decided to launch the system on a Friday then go home for the weekend, leaving nobody around to keep an eye on the house while it burned down.
Doesn't make any sense to me, and it just showed how disconnected both Bethesda and Valve are from the modding community.