「見える」 is not a transitive verb. It's an intransitive verb meaning "to be visible".　And 「見えない」 would be "to be invisible" So 指導力 isn't an object but a subject. 「指導力が見えない」 would be "the leadership is invisible". The potential form of 見る is 見られる. But potential forms of transitive verbs take が/は instead of を. So if you want to say "I can't see the leadership", it would be 指導力が見られない still using が.

が is used to indicate objects of POTENTIAL VERBS. 私は日本語が話せます。(Watashi wa nihongo ga hanasemasu. = I can speak Japanese.) をis used to indicate objects of TRANSITIVE verbs. 私は日本語を話します。(Watashi wa nihongo o hanashimasu. = I speak Japanese.) In addition, this sentence [ 政治にさっぱり指導力が見えない。] "emphasizes" what you can't see in politics that's why it uses "が" instead of "を". Hence, it is ”が見えない” and not "を見えない". For more details on the usage of が, please read my answer here: https://www.italki.com/question/417398 Hope that helps. 頑張って下さいね～　:)