He didn't hire assassins to KILL Abel, he hired them to act like they were, from the sound of it. He wanted to see the full extent of Abel's ability. The problem is he vastly underestimates Abel, which is normal, no one can imagine someone being this strong and knowledgeable in this day and age. Emerson's also been alone so long that he can only think of his own designs and desires due to everyone abandoning him out of jealousy, so he sees someone like Abel and what little social skill he had goes out the window - starts viewing Abel as an important experiment, running tests and observations.
I feel kinda bad for him, honestly. He could have been a great guy if his first attempts at being friendly hadn't backfired so hard and people been so vindictive and jealous. Common case of a victim lashing back out.