They found secret meetings between his close advisors (two of them) and Lybian terrorist in chief before his election (without the embassy being warned of those), they found documents saying Lybia put money aside to found his political campaign, Khaddaffi was the first leader to Visit Sarkozy after his election, they found Lybian money going toward France, but they "lost track" of the money (probably most of it was cash), and couldn't prove that this money was used for the political campaign. Since the only thing they could prove are those secret meetings, they decided that they would stay on the side of caution and only convict him of provable offense (in nonviolent crime, that's often the case to be clear).

I would be wary of going through the appeal court. The judges motivation make it quite clear they were _extremely_ lenient and chose to ignore how contradictory a lot of statement were, and the other cases linked to this. If he is convicted for "subordination de temoin" in the related case, it is likely that his sentence would be set to a longer time.

The fact that Sarkozy started the Lybian war was also outside of the scope of the trial, sadly.