The most important thing to defend against a hostile takeover is to guarantee overlap.

Let's assume the extreme of only 1 vote.
Assuming the community has 200kmvests to distribute, in the optimal case each of the top 20 witnesses gets 10kmvests.
However, that would be an optimal case, we know that a lot of votes will go to witnesses in the top 100 ranks and votes will be distributed unevenly.
Most likely the top 5 witnesses would have around 20kmvests and the bottom 5 more around 2-5mvests

Now anyone with some kmvests could distribute this to 4 accounts and could easily come in and elect 4 witnesses to block a hardfork.
Even worse, depending on the distribution, since there is no overlap, the person might even be able to vote in 10-11 witnesses.

So, currently with 30 votes, the community had to organize and stop voting for the 30-100 witnesses and assign their votes to the top 30 to combat the overtaking.

With infinite witness votes people could vote everyone they agree with and not just the top 30 they agree the most with.