This is an example of a Big Mess Construction:
- This is too big a mess (for anyone to clear up).
You'll find the same format in a number of other cases:
a. She made too rude a remark (for me to repeat).
b. She made so rude a remark (that we were shocked).
c. I’ve never heard as rude a remark (as that).
d. He doesn’t look the type to make this rude a remark.
e. He doesn’t look the type to make that rude a remark.
f. I wonder how rude a remark she could have made.
g. Don’t be offended, however rude a remark she makes.
— The Big Mess Construction
In every one of these, the adjective must come before the article for it to be grammatical.
There are numerous academic papers on the subject, but they're heavy with jargon and hard to summarize. In other words, the name fits.
The easiest explanation is: it's idiomatic.
It's actually been around for a long time. In an unrelated search, I discovered this quote from 1576 (via OED):
No man could be able to endure so colde, darke, and discomfortable a Nauigation.
— 1576 H. Gilbert Disc. Discov. New Passage Cataia vi. sig. E.iiijv