Because that's what happened
Which they didn't know at the time. And "At the time" is what I'm asking you. What reason did they have AT THE TIME THEY ABANDONED SHIP to remove the dilithium processor? Based on what they knew at the time or could have reasonably been expected to guess?
Not just taking control of a ship, and not just scuttling.
"Prevent them from taking control of the ship" is the purpose of scuttling. Discovery, being disabled, is in no danger of falling under enemy control. Salvage -- even military salvage -- is common enough that trying to prevent it is something you would only do if the leftover parts have intelligence value. Shenzhou is too old for this to be the case.
Likely screw the survivors? The show depicts ships with auto-destruct and even remote disabling features!
None of which have EVER been used to further immobilize a ship that was already disabled or wrecked. A dozen examples have already been shown to you of this being the case. Why do you continue to ignore them?
No, you don't burn your house down. You tell the house computer to disable or booby trap the place.
I didn't do that either. Is there any reason why I should have?
How do you know that they brought the telescope?
Because they're the only ones we know of who were actually present on the ship at any time between the Battle and Burnham's receipt of the telescope. Until we have evidence that someone else visited the wreck off screen, it's logical to assume the crew packed it themselves when they evacuated. And again, it was pointed out that they were in no particular hurry to do this, with the battle being over and the only reason to abandon the ship was its apparently irreparable loss of motive power.
As explained earlier, if a ship can be rigged for auto-destruct, then it should be easy to rig it for auto-disable or booby trapped. Starfleet can retrieve any components later if they wish.
As explained earlier, if my old house could be burned down, it should be easy to burn down or booby trap it so the global communist conspiracy can't use it.
So is there any particular reason to burn down my old house?
[The fact that, as you put it, Starfleet "neglected to destroy" what was eventually used given circumstances that are presumably "highly unusual" (as if it's abnormal for ships with crews to be left drifting in space for months), in exchange for retrieving something of no strategic value, only reinforces the point that it's a plot hole
It's not a plot hole. The crew of the Shenzhou didn't know scuttling the Shenzhou would be necessary. Characters acting on imperfect knowledge is a plot element, not a hole.
Romeo poisoning himself because he doesn't know Juliet is still alive is not a plot hole. Oedipus murdering his father and banging his own mother is not a plot hole. Picard taking a box of personal belongings from the Stargazer that happens to contain Bok's mind control device is not a plot hole. Gul Dukat beaming onto Deep Space Nine to and giving the computer his access code -- only to discover his code doesn't work and now he's as trapped here as they are -- is not a plot hole.
If Saru had known that the one-in-a-million scenario of a stranded Klingon warship needing their dilithium processor was going to happen six months later, he would have simply sabotaged the processor so the Klingons couldn't use it. But if he had known that, he also would have known that the boarding action on the Ship of the Dead would prove crucial to overcoming the cloaking device in the first place, in which case he probably would have painted a giant "get your dilithium processor here!" sign on the hull.
characters lacking common sense.
Common sense tells you that the Klingons have no reason to salvage a dead hulk for parts they can just as easily get from their own supply stores. Voq's situation only occurs because it is extraordinarily uncommon.
