This is because gods in that universe derive power directly from the number of people woeshipping them, right? So, yeah, the goddess of farmers makes sense as one of the most powerful, because there are a ton of farmers out there.
I’m not particularly familiar with the FR pantheon, but I would imagine a god/dess of death would prove quite powerful, particularly if people don’t just pray to them during a funeral rite, but also as an homage to deceased ancestors. Also, a deity of trade (which I’m pretty sure FR has—is it Waukeen?), as trade is very important and there are doubtless plenty of merchants and trade guilds.
While I think this is definitely true, there does seem to be a notable exception to that in Bahamut and Tiamat, right? They're both pretty powerful deities, but unlike other deities, their own races don't actively worship them.
There's probably some obscure lore in there that I don't know, I suppose.
It would make sense. Dragons get more powerful as they age, and seeing as Bahamut and Tiamat made some sort of proto-universe (The First World) which shattered when other gods tried to colonize it, resulting in all the different DnD worlds and timelines (as well as the two of them becoming eternal enemies, so I'd bet my boots that Tiamat wanted to kill anyone that tried to colonize her world, while Bahamut sided with the colonizers and protected them. Of course the colonizers ended up capturing Tiamat and tortured her until she had five split heads, and actually did overload and shatter the First World, also killing Sardior in the process, so perhaps it's not so hard to see how Tiamat went from creating a world to being the biggest, baddest and most far-fallen villain of all time)...
Well, my point is they must be really freaking old. Perhaps very little of their power has to do with being divine, and it's more just that they're nearly as old as the universe. The divinity just means they can't die of old age or be permanently killed, so they can (slowly) get more powerful forever.
The origin for the draconic gods is a bit different. Once, they were a whole, one.
In the dawn war, a primordial lord cleaved the arch-dragon deity in two. Those halves would transform into Bahamut & Tiamat, who would then team up one singular time, to bring down the elemental. And then they decided not to ever ever agree ever again.
That's the short story of their origin.