For a cause

I have two questions about the passage below.

(1) What does ‘for a cause’ mean? (I guess it means something like ‘in order to help others,’ which appears later in the same sentence.)

(2) How is ‘that’ in ‘plant the seed that ...’ used? I think, in terms of the sentence structure, this ‘that’ isn’t a relative pronoun but a conjunction and makes an apposition clause like (a) and (b).

• (a) They arrived at the conclusion that he way lying.
• (b) No one can deny the fact that she is a great musician.

Can the noun ‘seed’ be followed by an apposition that-clause? If so, could you give me an example sentence including ‘the seed that ...’?

Kids love it when their teachers open up a bit about their lives, talking about the positive behaviors they engage in on a regular basis, whether it’s a hobby or special interest, or even a sweet story about their own family life. If a childcare provider happens to mention that she loves to swim and is training for a triathlon for a cause, that will inspire athletically inclined kids to pursue their interests, and will also plant the seed that getting active in order to help others is a positive thing to do. When a teacher mentions a way in which she helped out a friend or a family member in need, that teaches kids about helping behaviors and how they can be applied in real life. Kids need role models, and often look up to the caregivers they see each day.