Iyer and GG didn’t want Vaibhav debut
Both GG and Iyer had decided not to make any change to the batting for the first three matches of this series. And Vaibhav was supposed to debut at the earliest in the fourth match. But the team management had intense discussion with the BCCI management who were unhappy with him being on the bench, not given a chance in the Ireland series and especially as they lost it as well. Because of all this there was immense pressure on them to give a chance as either way there is a sword dangling over GG - BCCI is considering whether to have split coaching for tests or just remove GG all together.
Under these circumstances, they had to give him the debut. That’s the reason you will not see any good moments being shared between Vaibhav and GG or Iyer. You have noticed that the cap was provided to him by Tilak when generally it is provided by the captain, the coach or a very senior member of the team and he is not any of these.
Source:
I am friends with someone who is a close relative of someone in the squad.