The importance of the point guard can be seen by looking at Houston this year. As soon as fred vanvleet arrived, the team started to get wins. It was a mistake for the spurs not to approach vanvleet more seriously.
But can we really attribute the success to the PG alone? I mean, they have a new coach, and not only Vanvleet who are playing well for the team, even Brooks are playing great basketball. The thing is, if Vanvleet joined the Spurs, he might also struggle as his teammates are young, doesn't have the experience in the playoffs, unlike with some of his teammates now, maybe Brooks to be safe which has plenty of playoffs already.
Spurs doesn't expect to be a playoff team with their current line up, they are still in the rebuilding process, so they need to be patient and make everyone play according to their rule, that's what we called great chemistry.