Even the theory of Crown Prince Sohyeon's poisoning is treated as a conspiracy theory these days

Among historical conspiracy theories, this was an event that was almost accepted as established fact,
and it is still perceived that way by the public,
but these days, the prevailing view in the historical and medical communities
is that he died of illness.
1. Bleeding from the seven orifices
This is the core of the theory that Crown Prince Sohyeon was poisoned,
but the medical community interprets this post-mortem symptom
as a typical sign of sepsis.
Looking at the records of Crown Prince Sohyeon,
there are many records of him suffering severely from diabetes
(frequent thirst and low body weight)<
(fainting after eating white rice, etc.)
Due to his eight years as a hostage in Shenyang, Qing Dynasty,
his chronic conditions worsened significantly,
and acute complications and sepsis are viewed as the cause of death.
2. The execution of Lady Kang and the persecution of the grandsons
Another core element of the poisoning theory is that
his wife, Lady Kang, was executed,
and his grandsons were all exiled to Jeju Island,
two of whom died during that time.
King Injo is criticized for being an incredibly cruel psychopath,
but because Crown Prince Sohyeon died,
the legitimate line of succession was completely distorted.
The first three in line for the throne were the grandsons.
In order to pass the throne to Grand Prince Bongrim,
he had no choice but to exile them, and two of the grandsons
died from an infectious disease.
(While he didn't kill them directly, it qualifies as willful negligence.)
The third grandson was later released from exile,
received royal treatment, and continued the lineage...
Lady Kang also had a strong personality,
and since she would never willingly surrender her succession rights,
it was obvious she would become a spark for future conflict;
thus, for the sake of the succession, execution was the only practical reality.
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In the end, it is widely accepted that Crown Prince Sohyeon did indeed die of illness,
and the subsequent ruthless treatment of his family
is interpreted as an exercise of royal authority
to ensure Grand Prince Bongrim's succession.
In fact, even after Grand Prince Bongrim became King,
he was plagued by legitimacy issues throughout his life,
and the Yesong debates during King Hyeonjong's reign after King Hyojong's death
ultimately have their roots starting here.
Anyway, Crown Prince Sohyeon died of illness (Medical view)
and the treatment of his family was inevitable (Historical view).
These days, this is almost the established consensus.