u/Daemon1997

Aegon hanged ratcatchers while Otto lords. If Otto can get away with it I am sure he would have no problem to justify the ratcatchers.

Also Otto was mad because ser Criston sent Arryk to kill Rhaenyra pretending he was his brother while Otto wanted to send Westerling to do the same.

In one hand ser Criston sent someone loyal and the plan was actually clever and on the other hand Otto wanted to sent someone who there was no chance to do that.

They didn't have eminence and they couldn't accuse him but what about in privet? Oberyn Martell didn't hide his hate for the Lannisters and he is even know for using potions.
If I was Tyrion he would be the first suspect that would come to my mind.

He did not appear in trailer nor in the posters or promo photos. It's not like he is meant to be the big reveal or a big character. He will probably appear in the few scenes and maybe will die in this season too.

And its not even an important character in the show. He did not exist in season 1 and had some mention in season 2.