Review of the Mad Emperor: Heliogabalus and the Decadence of Rome

The debauches sound wholly fabricated. I don't know why historians imagine they can pick out anything true. Even if an appointed official's name is corroborated somehow, there seems no reason to believe whatever was written about him or about why he was appointed.

We can be fairly sure Elagabalus was not well-liked by the literate class, and we can see what sort of activities they thought people would or ought not approve of.

We see similar behavior by historians on whether Jesus ever existed as a physical person. Almost all received documentary evidence is either obvious fabrication from often centuries later, or (e.g. in Pliny) acknowledged hearsay. The overwhelming majority of material represented as "early church", on any aspect, is clumsily forged.

The star exhibit supporting existence is a single paragraph in Josephus that every historian agrees was at least clumsily doctored by apologists. Many earnestly believe they can pick out bits of it not doctored, but the whole passage it appears in reads better with it omitted entirely. The most favorable judgment of it that can be supported is that nobody can prove none of it was in the original manuscript, and the "reconstructed" version reads a lot like Josephus.

There is no information to suggest why it would have been thought necessary to corrupt the original text, if it existed and read as "reconstructed". Statistically, the fraction of historians doubting existence is monotonically increasing, with no change in the evidence. That is actually progress.

It's no surprise that people were upset.