My theory is that Indra in this event is more benevolent then he'll let on.
In Vritra's interlude, she states that she will never be able to experience what it's like to grow and change the way humans do, and when she watches humans overcome obstacles, she's just living vicariously through them.
Now in this event Vritra's been robbed of most of her power and has become a child, and Indra hasn't given an explanation as to why he has her powers and hid them away. And now she's going on a skyfaring adventure with Arjuna and Rama to restore the sky and her powers.
Seems like there's a connection.