I kind of understand the overall meaning of "もっとも一等になればこそで," but I am not sure the exact meaning of "もっとも" and "ばこそで" here. Could you help me figure it out?
もっとも introduces concessive information. In other words, it's footnote to something that it is not as good as it looks. Here, the text seems to be glorifying entering a competition or finishing it in higher places. Then, もっとも comes in to deplete the praise for anyone that finishes lower than the first place.
Xばこそ emphasizes the value of doing X. I'd construe it has an underlying Xばこそ(意味がある).