Unlikely things happen. Two cases of rapidly progressing/late discovered cancer - what, precisely, do you mean by “turbo cancer”, anyways? - within one person’s social circle within a short time may not be likely, but at eight billion social circles, it is bound to happen to a good many people by sheer coincidence.
More concerningly, there are actual effects that could cause an elevated cancer risk, such as genetics* or the spilling of radioactive material or carcinogenic industrial chemicals**… possibilities ignored in favour of the conspiratorial scapegoat.
(And as a consequence, they suffer more misery, which in turn increases their desire for scapegoats… a vicious circle of the minions entrapping themselves ever deeper in the manipulations and exploitations of their overlords..)
* which reminds me of a previous speculation of mine that the antivaxxer belief that autism must be acquired rather than genetic may be rooted in part by the arsehole parents being afraid of having “freak genes” themselves.
** conspiracy theory: Republicans are pushing Covid-19 vaccines as the anti-panacea to cover up the effects of deregulating industrial and environmental safety.