Maybe he feels more comfortable being Dick in California with Anna...but thats only because she knows the secret. The only reason he is there in the first place is because of his assumed identity. If there was no Don, there would be no trips to California.
To be fair to Don, if you are working through the papers on an IPO without the knowledge of one (two? did roger know) of your 3 living named partners...that's kind of a dick move. Hard to get mad if he does something that screws it up if he doesn't even know it is happening.
No, it's pretty easy. While it's true Don did not know it was in the works it was a typical Don-decides-for-us-all-off-the-cuff move that tanked it. It was just a typical day in the life of Don Draper.