Drogon é mais experiente.
Há uma pergunta semelhante sobre SFF.SE com uma resposta bem resumida.
Drogon is the biggest
Drogon is essentially the big brother of the
three. He's the largest, potentially the fastest and most probably the
strongest; he's the alpha.
Drogon has Dany in the pilot seat
It would make a lot of difference
that Dany is the one riding Drogon, able to give commands, and steer
him better than the other two may.
Drogon has the most combat experience
Being Dany's main ride, Drogon
has experienced a lot of attacks, he has gained the most experience
under attack than his two siblings.
Viserion was hunted by the Night King
Olympic level javelin throwing
is an understatement for this guy. The Night King took down Viserion
as they were retreating with an epic throw of his spear. He's
powerful, that spear was travelling very fast, and hard. It pierced
Viserion exactly where it needed to to mortally wound him.
Rhaegal was injured already
In the scene where Rhaegal is shot down by
Euron's scorpion, we can see that Drogon and Rhaegal are flying in a
tight, low and slow formation. Rhaegal is visibly injured, his wings
torn from the Battle of the Long Night. This makes him slower, and a
much easier target.
Besides, Euron had the element of surprise; he could take his time
with his shots and make it count. Notice how once alerted, Drogon was
able to evade the rest of the arrows?
Drogon was in fact hit once Recall in the Seventh Season, Drogon is
hit by Bronn's scorpion, severely damaging his shoulder. So he's not
invincible.
Why is Drogon so much better in battle than Rhaegal and Viserion? - SFF.SE
Quando Rhaegal é morto, parece evidente que Dany não estava esperando os Escorpiões nessa magnitude ou no mar e ela também já estava com raiva de perder um dragão, por que arriscar o outro?
No S8E05, Dany não estava olhando para intimidar, estava procurando negociar (ou pelo menos Tyrion a convenceu a fazê-lo).
I don't want to see this city burn. I don't want to hear the screams
of children burning alive. No, it is not a pleasant sound. I-- I don't
want to hear it. Help me save this city. My lord, I am only a
mouthpiece for our queen. TYRION: Your queen. Cersei is Queen of the
Seven Kingdoms. You are her subject. Her reign is over. You understand
this. Help her understand it.
Game Of Thrones, Season 8 Episode 4 (The Last of the Starks)
Um dragão andando por aí teria deixado todo mundo tenso e provavelmente diminuiu suas chances de negociar uma trégua com sucesso. Além disso, se Drogon estivesse sentado na linha de frente com Dany, e eles tivessem escolhido atacar, ele seria um alvo fácil para as dezenas de escorpiões. Portanto, nenhuma vantagem estratégica ou diplomática teria vindo de Drogon sentado à frente e no centro.
Em S8E05, Dany (e Drogon) sabiam o que estavam entrando e agora estavam se preparando para fugir dos tiros dos escorpiões e sabiam que não viriam pela frente, mas iriam direto para o meio e passariam o máximo de tempo possível circulando. Frota de Ferro para tornar a mira o mais difícil possível.
Portanto, nenhum poder de Drogons não foi subestimado, ele estava simplesmente sem a preparação e a experiência até S8E05.