He was the most prolific mathematician of all time (most published papers) by an order of magnitude. His papers launched entire subfields of mathematical inquiry. He dedicated his life to math in a way that most people could never dream of dedicating themselves to anything, having no home or family or possessions and instead doing mathematics all day every day. These seem like good reasons for him to be popular among mathematicians.

"The Man Who Loved Only Numbers: Story of Paul Erdos and the Search for Mathematical Truth"

Is a humorous non-mathematical book about him. Erdos was a funny and strange man. He was the most prolific co-writer of math papers.

He didn't have a home, but would just pack his bags and sleep over at other mathematicians couches around the world. He would ask about their math interests and problems. Erdos often had some great insights and unusual perspectives about it. He would talk about math with them non stop, until they could take no more. The other mathematician would often write a paper about what they had discussed, and Erdos would be sent on his way to the next mathematician.

When he discovered or heard about some very beautiful proof. He would say this proof was "from The book". As in the book that God wrote. He also called God the supreme fascist.

Erdos dint sleep much and didnt care about things that where not math. He couldn't tie his shoes, liked to tell silly jokes, and was a virgin. He was also on amphetamines most of the time.

I think part of it is that Erdos worked with an unusually large number of people, at an unusually large number of places. Another reason is that he was quite eccentric, even by the standard of mathematicians. There are so many stories about him, which led to a sort of legend, and that led to all the books and documentaries. Finally he was around at a time when discrete math was gaining traction as a de facto area of mathematics, and he made a great number of contributions in that area. For example the probabilistic method he popularized is a cornerstone of the subject nowadays.

Whether or not he was disproportionately popular depends on what you feel it should be proportionate to. I reckon he is more famous than similarly important figures in other subfields of math. But few mathematicians have worked with and influenced so many people.

If you really want to know the actual reason the title reads "new erdős paper" it is this:

https://en.wikipedia.org/wiki/Erd%C5%91s_number

obviously this is not an actual new erdos paper, but without these shenanigans everyone's erdos number would slowly but surely increase, as first nobody new could have co-published with him (too young) and soon the same applies to his co-authors.

while it might have been cute back in that era, today I think it should be treated as a historical thing.