Because if Red Knight didn't have the ability to create miracles, she wouldn't be much of a deity. It's the scope of those miracles that differs.
If I may mug your analogy.She can grant spells to her followers. They are limited in scope by its portfolio and in power by her rank in the divine hierarchy.
That's like asking for Robin to have the same power level as Batman.
To put it another way, Demon Lords/Princes of Hell are pretty low on the deific totem pole, and yet they have the juice to power high level evil cultists. Because if they didn't, well, how else would they get anything done? Get a few 3rd level cultists to summon a nasty demon, I think not.
But it isn't saying that both have the same power level in an absolute sense, just that they can both grant all spell levels. I'd expect even a lesser god to be able to grant(cracking open my 1e PHB here) wind walk, or gate, or control weather. The Red Knight might have less power than Tempus, but she could still be able to grant spells, much in the same way that though I am less rich than Bill Gates, I can still lend a buddy 5 bucks, and my 5 bucks will have the same value as Bill's.Why are you assuming that both dieties have the same power level to share, if such power level comes from the number of believers in the first place?
Let's take Tempus, major diety and god of war, battle, conflict, warriors, etc. He is a very powerful god, since war and battle are happening all the time.
Now take for example Red Knight, semi-goddes of tactics and exarch of Tempus. Would it make sense that a diety that servers a more powerful beign and has a narrower portfolio to have the same level of power to distribute to its followers than such diety?
All this in addition to weaker church, fewer power centers, fewer political power, etc.
She can grant spells to her followers. They are limited in scope by its portfolio and in power by her rank in the divine hierarchy.
That's like asking for Robin to have the same power level as Batman.
Let's summarize:
Relative to each other, deities vary wildly in power-level. Analogies abound.
Relative to mortals, all deities are literally godlike. Spells for everybody!
I think we're done here.