You see two different values, One value for Acquisition Program & a different value for Acquired by.. What do they mean and
Acquired By specifically means 'this program was responsible for creating the lead record'.
Acquisition Program is an attribute that you are able to change, but Acquired By is something controlled by the system that designates when that program is directly responsible for creating the record.
For example, if you had an SFDC Campaign that was synced to a Marketo program, and you added a lead to that Campaign, the lead would be synced down to the Marketo program. You could then use a Smart Campaign to set the value for Acquisition Program. However, the program would not receive Acquired By credit because the lead came from Salesforce and not from the program directly.