I think as a fan base we have summarised it quite well, probably could have had a booking before he did but Gakpo carried on (if he had gone down it would have been a yellow) and then rightly booked and then a potential second booking not given.
I believe a few things went in his favour, Fabinho not being booked, close proximity to the first booking and that it would be a second booking.
It was the right decision not to send off, but I can understand why Liverpool players asked the question and imagine if it was Fabinho we would have been shouting for a red from the stands.
Gakpo and Fabinho possibly should have had a yellow, but some games are reffed differently and I think this ref didn’t want to be too card happy.