These merchants/innovators were not dumb. There were a number of reasons why they chose Charlton. First was because they saw him working with Edward, rather than making Edward work for him, like any other nobles. He had the status and lineage, but despite all that, he still treated people with dignity.
Second was for who he was. He was the son of arguably, the second most powerful man in the kingdom. The Grand Duke of Suffox was a war hero who has the control of about 40% of the kingdom's military force. He's married to the king's sister which automatically put him under the monarchist faction, however, it was no secret that some members of the radical faction were his brothers in arm.