The supply curve getting flatter can happen as a result of increased production capaciy.
When producers or suppliers have the capability to significantly increase their production in response to price changes, the supply curve becomes flatter.
This typically happens when there is excess production capacity or when it is relatively easy and cost-effective for producers to ramp up production.
For example, if a factory has unused production lines and can quickly hire additional workers and acquire raw materials, the supply curve for the product becomes more elastic.
If suppliers can easily switch between different inputs or resources to produce the same or similar goods, the supply curve becomes flatter.