Bem, isso é explicado nos romances posteriores (os personagens basicamente repescem as situações anteriores de Seldon Crisis, bem como suas soluções), então eu não quero estragar demais para você. Em cada caso, conforme o desenho de Seldon, a resposta é quase inevitável.

Eu não os li em poucos anos, mas, pelo que me lembro, os primeiros pontos da crise:

(Cabeçalhos para lembrá-lo sem mostrar o spoiler, se for o suficiente - não quero estragar a diversão, se você reler :))

Balanço de Potência

Basically, they didn't try to fight them, but they made sure the enemies of the Anacreonians knew what was happening; their enemies couldn't risk one group having access to nuclear power, so a stalemate forced them all to leave the Foundation alone. I believe this is the 'obvious' one you reference.

Religião

Next they instituted a 'Religion' behind technology and used that to make fighting the foundation a 'Sin' with demonstrable results; the trained techs on other planets didn't really understand things, just know how to use them. The foundation retained the ability to put them under Interdict, at which point all of their foundation technology ceased working.

Comércio

The third one was simple; dependence via commerce. The Religious angle had played itself mostly out, as worlds were aware of it. But Hober Mallow stuck to the idea of trade alone protecting them. They provided a product that couldn't be had anywhere else, was better than what was available elsewhere, and forced the enemies into dependence on their product. A little 'planned obsolescence' and they had enemies that couldn't afford to make war against the Foundation, as they needed Foundation supplied tools to do so with.

Ah, devo mencionar - esses são os pontos de crise EXTERNOS. Também havia internos em cada Crise de Seldon, mas não acho que você estivesse perguntando sobre eles.