Relates to MC-154098. Drowned on land during the daytime will not defend themselves from attacking hostile mobs, even if they are protected from the sunlight. Instead they just stand there and allow themselves to be killed.

Once the night begins however, the drowned immediately begin attacking the hostile mob. This behavior is unintuitive for players (why would a drowned suddenly start defending itself based on the time of day?), and ruins the challenge of the drowned mob. It also badly breaks custom maps as well as most drowned mob farms.

How to reproduce:

1. Create a roof of arbitrary size that prevents drowned from burning
2. Spawn in any number of drowned. The effect is more obvious in groups.
3. Make sure the time is set to day with /time set day
4. Summon any mob that would attack the drowned, such as a Johnny vindicator or an iron golem.
   → The drowned do not react as they are killed, and nearby drowned don't attack.

    /summon iron_golem ~ ~ ~ 

5. Change the time of day using /time set night
   → All of the drowned immediately aggro and attack the hostile mob.