The Grail had only been defended for 4 days at that point. I simply put all the peasants on horses. And I fought against Agrail near the fort. He attacked me himself. I just collected all the chests with money and spent it all at the trading post. By the way, there were still peasants left. But I didn't build any angels at all.
There are enough archers at the very beginning. And that's enough. You can turn them into crossbowmen, and with a blessing, they tear through everything. But griffins are a double-edged sword. Firstly, they are reached quickly because they are slow, and secondly, you can't know where this creature will land after a battle dive; how many times did it trap the cavalry?

Well, 4 days of defending the Grail is still 20,000 – a very significant amount. In addition, a trading post with a good exchange rate is an extremely rare building, and there are also quite a few resources and mines on this map. You won't find all of this on a random map. You won't be able to start training before the second week, and by the second week, after building everything necessary, there will definitely be very little money.
And as for the archers, what will you do with them if the enemy is shooting? Or even if they just run fast? For example, against dryads or furies? That is, you will most likely win, but there will be losses, and after a few days of fighting, there will be SIGNIFICANT losses, and development will slow down.

P.S.: We are probably talking about different Agrails. The heroes who attack the city don't count; their armies are weak. I meant the Agrail that appears at the bottom at the end of the mission. Moreover, on the next turn after this, the mission ends, so he couldn't have attacked your city.