In the past, Jack would have intervened and done everything to help his grandson quickly chase a girl. After all, it would be quite embarrassing if his own grandson didn't know how to chase a girl, and he'd become the subject of mockery. But now, Jack couldn't possibly do that.
Previously, Benjamin had a haughty attitude, as if he looked down on Martina. However, now he had finally realized the need to be more attentive. This situation was a result of his own indulgence and neglect, and given that, he had no reason to continue to micromanage things. He could simply act as if he hadn't seen anything.
Jack wouldn't completely ignore everything, but he couldn't be as overt as before. He would only secretly support them and believed that these two lovebirds should be left to their own devices. This approach might help their relationship become purer and hasten their union.