Why don't the miners just take profit from our coins and make the coin worthless? You own a very valuable thing and you want to go to holiday without it, but there is nobody who you trust and who can look after the thing. So you take somebody unknown to guard it. You pay him a fee hoping he doesn't run away with the valuable think. How much would you pay?

I think you should pay for the fee minimum the value of the valuable thing!

But now to bitcoin. Do the story again:
You own a very valuable coin which is guarded by somebody unknown (the miners). You pay him a fee (mining profit) that is much less than the value of the coin (market cap of bitcoin). Why don't the miners hold short positions on the coin, bring value of the coin down with a large majority attack which destroys any trust in the coin and go with benefit from the destruction?



I asked this fundamental question about bitcoin in a stricter way 2 days before in this question and similar in this question and there is also a bounty for an answer, but there is only less interest and no upvotes and no good answers. I think the question is fundamental, and so I tried to do it in an easy analogy now.
Because miners do not actually own/ or have access to the bitcoins which are being spent in a transaction.

They simply choose a number of transactions which have valid signatures, and put them together with the hash they created/solved, thus creating a valid block.
See https://en.bitcoin.it/wiki/Block_hashing_algorithm for more information.

The person that owns the private key owns the bitcoin, which (unless you share it ofcourse) would be something miners, or anyone in general, won't have access to.

EDIT:

There's currently ~12.000.000 TH/S, In order to gain 51% of the hashpower, ( which is needed to always be faster, thus control the bitcoin chain), you would atleast need 12.000.001++ TH/S, lets say we would generate this power with an Antminer S9+, currently the fastest, (i believe?) which has an average speed of 11.5TH/S

12.000.001TH/s / 11.5 = 1043479 Antminers, which would cost a total of 
1043479*2000= 2.1 billion$

If you're willing to spend that much money just to short bitcoin, you have to ask yourself if it's going to viable, and profitable.

Even if there's a majority attack, miners still can't decide the protocol rules. See What can an attacker with 51% of hash power do?

as to what is actually possible with a 51% majority of the hashpower.

You could then speculate on the price going down, but then again, it might not, leaving you with extreme losses.

Also, you would probably be able to earn way more by simply mining the majority of the blocks and its fees.. 25 Bitcoin every 10 minutes ( since you have the majority) = 250k$ every 10 minutes. ( At the current exchange rate. )

250.000*6*24=36.000.000$ in blockrewards each day alone. 

So, i'm not saying that you can't theorethically making profit shorting it while trying to destroy it with a majority hashpower, but that there are probably better options.