I think this is the right decision made by Leverkusen management, they took quick steps to build the team in a new direction because it was clear there was no progress whatsoever with Ten Hag even the Leverkusen team was much worse after being coached by Ten Hag so even though it was only the beginning of the season but I think this decision was quite right even since the beginning of his arrival I was very doubtful because Ten Hag was a failed coach in the past so it was difficult for him to find his confidence again.
The club was not quiet in the transfer market after losing many crucial players in the summer, they spent quite a lot recruiting new players so the least they could expect from Ten Hag was to win some games even if not all but it happens that the results were consistently negative and poor even with the first three games of the season so I don’t blame the club at all for their decision to sack him because he didn’t shows signs of improvement.