They are assuming/hoping/manufacturing the fact that the money came from a campaign account, and not a personal account, and THAT would make it improper... but in an actual legal system, there would need to be proof that it came from a campaign account, AND that the President specified to Cohen that the money come from the campaign account (usually requiring something more than he-said-she-said), in order to meet the requirements for the illegal use of campaign funds.
The Left is getting waaaaay ahead of itself, as usual... and hoping that nobody notices that the details matter. The drones of course, do not care one bit... they have something else to scream at the clouds about, so they're happy.
Politico tried claiming that the money (whether or not tied to campaign funds) itself was illegal as it tried to influence the election.
https://www.politico.com/story/2018/05/03/trump-cohen-payment-explanation-566044
The payments to Daniels, which was made days before the 2016 election and went unreported to the Federal Election Commission, could constitute a violation of federal election law if it was made in order to protect the Trump campaign from political damage.