These are good example of the reliably dumb conservative having real trouble understanding simple things.
The straightforward facts are someone mailed what appears to be trump's 2005 1040 to David Cay Johnson, who then fwded it Maddow who reported on this, though arguably overselling it. The white house confirmed it's legit, and by the "client copy" stamp it seems to be sourced (originally at least) from trump himself.
It's hard to imagine what could be so confusing about what can't be a simpler sequence of events, but conservatives are rather good at outdumbing themselves.