The springtails will not harm your plants or soil. The are benign. There is really no need to concern yourself with them.
As for why they showed up, you may have some raw soil amendments left in your soil that aren't fully "cooked" yet. Springtails are detritivores, meaning they feed on dead, decaying organic material. If your soil mix is already fully degraded/composted, it will not provide them a food source and they will likely never show up in the first place. Same reason they'll show up in an overfed worm bin, but will leave after the worms have caught up with their food supply and there is no longer decaying organic material for them to eat.
In simple terms, they are degraders. They show up when there is organic material to degrade, and leave when it's all degraded. If anything, they are helping your soil by degrading residual amendments that didn't fully break down while your soil "cooked".