Of course the game is easier in the previous biomes once you gathered all the resources to make it to the next one. That's just... how most games work.

And you may have just been lucky, because you got an "easy" seed. There are hard seeds out there, where everything is not so easily packed together. I had to travel far to find my first little swamp island and it only had one crypt with little iron in it.

So a lot depends on the seed. Try another one or look specifically for hard seeds if you want more of a challenge.