The answer would be that they're placing better than there peers, not worse.
I simply don't believe that the situation is as you describe, or that it's prevalent/widespread for hiring managers anywhere to reject frum candidates on the grounds you mentioned. Your vague, unverified to anyone but you, anecdotal evidence doesn't sway me. I know it's not true at my company, and the large numbers of frum professionals at big 4 and midsize account firms, major law firms, financial institutions and other companies employing professionals seems to indicate that it's not true elsewhere either.
Placing better?! Halevai!
Don't believe me, but I'm speaking from inside knowledge and first-hand experience. I went to college, went through recruiting season there, then went to law school, and went through the recruiting season there as well. While I personally have a job lined up (BH!), I have many frum friends who are brilliant and highly qualified who remain unemployed and are having a very difficult time finding a job. Yes, many big firms have frum employees, but the majority of them are from the older generation (I know it's relative, so for clarification purposes, I'm referring to the baby-boomer generation and above) who apparently didn't have the same attitude towards work as those of us who are younger.
Finally, and I apologize for being so blunt, but based on how your post was riddled with spelling and grammatical errors, I have a hard time believing that you have much of a connection to the large accounting/law firms and large financial institutions that you refer to. I'm a part of that world, and the things that I'm saying are unfortunately very true. I wish that they weren't.