I mean, you're right that such a setting is pretty hard to barricade effectively, especially when anyone without a uniform could go in/out as "supporter" and "visitor".

Like the other commenter said, they could have built up a high palisade all around, tho not sure most occupiers were into this type of stuff...

The goal with occupying the place was for stopping the diggers nonviolently. Which could have worked if the occupation would have lasted longer. So unless there's a re-occupation of sorts, or the German government suddenly backpedals, the outcome of this battle is sadly yet another activist failure.

With a level of awareness having been raised. But...