The "big deal" here isn't the affair - that happens all the time and if he were dating an employ or something boring like that we'd probably never even hear about it.

The problem is the spying and Chinese influence - which doesn't happen all the time and is a big deal because he runs the biggest chip company in the world at a time we're trying to keep that tech away from China.

Security clearance applications have a whole section asking about extra-marital affairs, money problems, and whatnot precisely because spys use those types of things to bribe, blackmail, and pressure people. It sounds like a cheesy Cold War spy movie - but it happens in real life, as we're seeing.