Indeed. The same thing applies to the 9/11-was-a-hoax crew - remember how some of them were claiming the attacks had been faked as a pretext to introduce repressive legislation, the Patriot Act supposedly being a harbinger of worse things to come, black helicopters whisking dissenters off to FEMA concentration camps and so on.
Similarly, Sandy Hook and other firearms massacres were seen by the more extreme loons as hoaxes that would give the US gubmint an excuse to take away people's right to bear arms.
But Columbine took place 22 years ago, 9/11 was 20 years, Sandy Hook 8 years... how long does it take before a hardcore conspiraloon admits s/he may have been wrong?
This may also apply to the anti-vaccine crew - if they fear the long-term effects of the vaccines won't manifest for several years... (a conspiraloon hoax doing the rounds a week or so ago claimed that Prof Luc Montagnier - of HIV discovery fame - had stated in a video that everyone who had been vaccinated would die within 2 years. Needless to say, in the video clip they were spreading, he said no such thing
)