I agree that from the perspective of a business owner this would seem very normal. "I need legal services for X, and I happen to know and trust a very good outside counsel for this" is very normal. Additionally, law firms have super robust conflict of interest policies so you can expect this would have been reviewed in details.

However, I think this story brings up two important topics:

1. It is important that high level government officials avoid not just actual conflicts of interest but also the APPEARANCE of a conflict of interest.

2. The Trump administration has taken a much more liberal approach to conflicts of interest than most admins, and this has undermined trust in government. The fact that this story got people so riled up is a great illustration of it. This is not good for the country!