You're right, I should have said that the chances are very very x 10000 slim.

Even compared to other closed nations, the n. korea's communicative data provided to geopolitical analysts are absurdly limited. So the one who's willing to or need to look beyond what ap or/and reuters publish would need to study their systems and history first to understand their current affairs faster and better.

Let me specify why many believe that the probability of kim jong-il's demise being an assassination is "very very x 10000 slim."

First,

until recently (the late 2016, more precisely) people of kim jong-il's so called paektu bloodline had a total grip on n. korea's all three major factions (the old revolutionary, hyper pro sino military generals, and the high echelons of bureaucrats in the workers' party). Those were the times when paektu bloodline people occupied more than the 90 percent of "positions that matter."

Second,

until aug. 2017, russia's svr rf was providing 'daily' intelligence + necessary resources for n. korea's top eight's security. This measure came from kim's distrust in some factions of n. korea + 'chinese people,' probably due to his father's dying wish ("Chinese people are our thousand years' enemy.").

Several accounts agree that kim had started to 'try to get putin's attention' even before putin became the head of the security council. Once putin agreed, in return kim was said to have 'helped' with disclosing the ccp's opioid/fentanyl 'exporting' routes to russia and he let russia use nampo and chongjin harbour.

And said measure turned out to being highly successful (?) was at the very least 'bothering beijing.' Even the ccp generals back pockets.

Third,

both of the brzezinski faction and the jarrett clique were still supporting kim 'with actual means' and in fact they're the ones who made sure kim jong-un's 'safe and peaceful enthronement' from (hyper) pro sino factions in n. korea. -- This sentence probably confuses people because said two groups are known for being pro beijing. But as you know, in the geopolitical realm, nothing is black and white, and there is never just one.

The rumour was that Kim jong-il's blackshirts were carrying out the eur super counterfeit project for the jarrett clique (and the genie energy faction), and it continued after 2012 (until 2017).

Fourth,

early nov. 2011, russia's an-148 landed in pyongyang with swiss medical staff and equipments, and eight more of an-148 were said to circle around the class b airspaces of pyongyang, wonsan, kaesong, chongjin, hamhung, and nampo between nov. 2011 and feb. 2012. What does it mean?

And lastly,

bonus things to consider: When kim jong-nam died? Feb. 2017. What happened in 2016 in the us? What was kim jong-nam in charge of when he's alive? The room 39. The faction in n.korea that controls the weapon deals and drug, especially fentanyl, production & trafficking via the ccp. Edited to add: And when the us admin allowed the following disclose: kim jong-nam was a cia channel (or informant if you want) in n. korea? June 2019. A couple of months after a supposedly 'hidden tv camera' caught kim jong-un having a smoke break on his train journey to his summit with Trump. What does it mean? What happened in the 2019 hanoi summit? How? Why?

Conclusion:

It's highly x 10000 probable that kim jong-il died from natural causes because many of dominant factions wanted him to keep going with what him and factions closed to him were doing. And kim's safety had a solid reassurance by one of the top tier intelligence agency(s).

Another edited to add (and probably last :p I need to get back to work.):

The second and third points above belong to the reasons why many believe that the probability of kim jong-il's demise being an assassination is "very very x 10000 slim,"

because the brzezinski faction and the jarrett clique were the one who 'destroyed' the bo xilai faction in order to put the xi jinping's princelings in power.