Jogi Low really should have been sacked earlier. But he had the World Cup title and several final and semi-final appearances to his credit. That's why he had a lot of credit, which was used up at some point. Hansi Flick didn't have that, which is why he was sacked sooner, albeit justifiably.
In fact, I also think that Barca is a hell of a job with this situation the club is at the moment. You have to build the team from scratch, just like Klopp has done with Liverpool since 2016. Hansi Flick could be a good candidate for that.
I think it wasn't only credit, it was networks that he built over time. After all the national teams around the world owe the people of that country a reasonable performance. Loyalty should have its limits, but like in all national football associations it is all about the networks that someone has and whether people who take action against someone else have to fear consequences later down the road. Fire Low and then he becomes a person in charge? Maybe not so good for the people who fired him.