That clause is a nominative absolute (see Wikipedia). The meaning is clear if we rewrite it as a separate sentence:

There was also a donation event. The proceeds were to be applied to provide food for the homeless.

"Is to be" is an idiom used to give commands or describe plans (see Britannica). The latter meaning seems more likely here:

There was also a donation event. The proceeds were planned to be applied to provide food for the homeless.

On its own, the sentence also implies that this plan was followed, but that depends on context.

Nominative absolutes are more common in very formal writing. But this one is convoluted by any standard.

That clause is a nominative absolute (see Wikipedia). The meaning is clear if we rewrite it as a separate sentence:

There was also a donation event. The proceeds were to be applied to provide food for the homeless.

"Is to be" is an idiom used to give commands or describe plans (see Britannica). The latter meaning seems more likely here:

There was also a donation event. The proceeds were planned to be applied to provide food for the homeless.

On its own, the sentence also likely implies that the plan was followed, but that depends on context.

Nominative absolutes are more common in very formal writing. But this one is convoluted by any standard.