The user suggested that while Varys was sentenced to death soon after the scene, his spy may have still carried out the plan to poison Daenerys.
Straight up poisoning the queen would be a terrible idea. He knows how much Jon loves her and, though it would mean he will have to take the throne, it wouldn't end nicely for him after Jon figures out what he did. A better plan would be to push Dany into madness early, letting it loose on King's Landing and showing everyone a Mad Queen, which is exactly what happened. How? Basilisk's blood.
Basilisk’s blood is a poison mentioned by Oberyn Martell in the A Song of Ice and Fire books which "produces violent madness".
However, it doesn’t feature in the TV series.
The user argued that the poison would help justify Daenerys’ sudden change and give Varys’ story a better ending.
This would justify the sudden descent into madness she took in such a short time. It would also give Varys a more meaningful arc.
A fan on Twitter also pointed out that the scene could have been a call-back to season 1.
ICYMI, Varys totally tried to poison Dany at the beginning of the episode. The callbacks to season 1 are amazing:… https://t.co/FnWLKi2DPQ