Why did Wu Bofan say that 2019 was the "Year of Paralysis" in his "Friends of Time" New Year's Eve speech in 2020?

Why did Wu Bofan say that 2019 was the "Year of Paralysis" in his "Friends of Time" New Year's Eve speech in 2020? This was because some challenging philosophical and scientific problems such as the "Paragon of Time" and the "Paragon of Measuring" occurred in 2019. One of the most famous ones was the "time paradox", which involved the passage of time and the influence of the observer. To be more specific, this contradiction involved a problem called the grandfather contradiction. According to this contradiction, if a person time traveled to the past and killed his grandfather, then the person could not kill his grandfather after returning to the present because his grandfather was already dead before he killed his grandfather. This question sparked many discussions about time travel and parallel universes. Wu Bofan mentioned this problem in his speech and thought that 2019 was a challenging year because the problem became more obvious and complicated. He also said that the 2019 question might inspire people to think and explore the nature of time, which would help advance science and philosophy.