After watching the testimony I've come to the conclusion that there could be several possibilities
1) Trump legitimately didn't know what he was doing was inappropriate. This narrative is currently being pushed by Paul Ryan
2) Trump knew enough to know this was entirely inappropriate, but he did it anyway. This narrative is backed up by the fact that he asked everyone, including Attorney General Sessions to leave the room.
3) Trump was attempting to stop an ongoing investigation because he did not want them to find out whatever there is to find out. Here we have lots of smoke but the root cause - if there is one - hasn't been made public.
I've listed them in order of severity. Starting with (1) - this is worrisome because it suggests that the POTUS doesn't have a basic understanding of how our government works nor how his actions would be interpreted. The current defense that "he's inexperienced, it's ok" rings hollow to me, and it suggests that we should excuse his actions as an innocent newbie mistake. Two problems I have with this - one not one single person of at least a half-dozen high-ranking people (including the US attorney general) made any move to stop this closed-door meeting. second, "not knowing better" is not an excuse. I'm reminded of the pathetic first attempts of managment to shrug off sexual harassment claims saying 'what, i didn't know what i was doing was inappropriate - i just made a comment about her bra". Ignorance is not a defense for something that should be obvious.
(2) More troubling is the idea that, even though there "may be no 'there' there" DJT knew at some level that his requests were on shaky moral ground but he pressed ahead anyway. In other words, he's so convinced that nothing below-grade happened that he just doesn't give a damn about how he goes about trying to end the whole thing. This involves an incredible amount of hubris ("Flynn's a great guy - I'm sure there's nothing there even I don't know about") and a complete disrespect for independent investigations. At a minimum it suggests that DJT won't even consider the possibility that the Russians may be craftier than at least one of his staff.
Finally there's the most troubling option (3), that this is in fact at attempt to obfuscate the truth. Not much was learned from this hearing to put this theory to bed, but nothing Comey said confirms it either. one interesting factoid is that Comey called out the NY Times expo as being largely false, but as expected would not say what exactly they got wrong nor what the FBI knows (or knew at the time of his firing) - for that we'll have to wait for when/if Mueller makes his report public. I'm still deeply troubled by this option, as there's just so much damn smoke. But, is the smoke largely the result of arrogant rookie pols falling into the laps of seasoned Russian opporatives, or is it more deliberate and sinister.
I guess we'll have to wait and see.