Seedorf challenges Hanson for the high ball that’s why his headed clearance is not very good and falls to Whyte, and his momentum carries him to where he ends up.
If you look at where he is when Whyte strikes the ball he is not in the keepers direct line of vision and as has been previously said once Hanlon touches the ball he could be deemed to be onside.
The linesman does not put his flag up straight away and IMO the ref and the linesman new that the ball took a deflection but did not know who it came off and erred on the side of safety and just gave offside.
It’s over now some you win and some you loose just hope the next tight call goes in our favour