A few thoughts.
I don't know how these drivers are paid, whether a full time contract, or pay as they drive, but I assume advertising duties above and beyond being a walking billboard are part of whatever contract they have. The sim racing could be put to them as part of their advertising duties when there is nothing for them to do to earn their money, or possibly any money at all atm. I would hope that any real life racing driver would have the option to not take part, but if they have chosen to be involved, or had no choice, then they take it seriously as they would any task an employer gives out. I would assume that a morals aspect would be mentioned somewhere in their contracts too.
After the American driver (can't be bothered to find out his name) was rightly sacked for the racist remark, I would imagine that the employers of any drivers involved in these sim races may have had a word or two about not bringing them into disrepute in any way, seeing as most of the drivers are more visible than they would be in a real car race with possibly just a camera over their shoulder. With all that in mind, what Abt did, for whatever reason, is not following the orders of his employers. Possibly not adhering to his contract. And bringing said employers harm to their reputation by association.
That Abt doesn't seem to think it is serious doesn't help people having too much sympathy for him.
Some people have said that it is rich of Audi to be pulling someone up on being deceitful, given the recent corporate history of the Volkswagen Audi Group. I would think that their hardline stance may have something to do with that. They now want to appear as squeaky clean, and an employee/driver found to be cheating, whether it was real racing, or simulated racing, is something they have to be seen not to tolerate.
As for the fine and being suspended being enough of a penalty. I think the Abt's father sponsors the Porsche Racing team, so money may not have been as big a penalty to him, with money in the family, compared to other drivers.
His reaction to what he did may have contributed to him losing his job at the end of it. There may be other things going on in the background, but whilst this is not as serious as the racist remark in many ways, that was at least said in the heat of the moment. This was done with planning, a lot of planning, and possibly also breaking quarantine/social distancing rules from wherever he was streaming from by getting the other driver in.
I would hope that Audi would have taken the same stance if Abt would have been the fastest driver on the grid, and leading championships, but who knows.