You probably need to place your own outpost the same turn you destroyed the other one. Which means it needs to go to a different tile, where another army of yours needs to be waiting. Relocating to the same tile as the old outpost is available afterwards, if you want that same location.

You can but it's a game of click. The first who click to put the new outpost, won.

This needs to be reworked. This is a strategy game not a fast click game.  :)

I'm not following. You're spending resources to place a new outpost, which he can then immediately raid for more gold. Where's the benefit?

When he post an outpost, it cost him 5-15 influence, which is not much. The other player need to bring 3-4 scout to bring down the outpost in 3 turns.
3-4 units is a lot, you need to build them, bring them.

So it's vastely more easy to put your outpost and hide yourself in the region or near the region. And you can't chase the scout while you are raiding.

This is why the 3 rules idea would solve logiquely this problem.