Learn Finnish: Kunpa olisimme ennakoineet tämän tilanteen! - If only we had anticipated this situation!

Because this sentence expresses a regret about the past. Kunpa ennakoisimme is the present conditional, meaning "If only we anticipated (right now or in the future)". To say "If only we had anticipated", you need the past conditional: the auxiliary verb olla in the conditional (olisimme) plus the past participle plural (ennakoineet).

Can I use kunpa without the conditional mood in a sentence like this?

No, kunpa (meaning "if only" or "I wish") strictly requires the conditional mood because it inherently sets up a hypothetical, unrealized wish or regret. Saying something like Kunpa olemme ennakoineet using the standard indicative mood would be grammatically incorrect.

Why is the object tämän tilanteen in the genitive form rather than the partitive (tätä tilannetta)?

The verb ennakoida (to anticipate) takes a total object when the action is viewed as complete. Because this is an affirmative sentence and the regret is about fully grasping this specific situation, the object takes the genitive ending (-n). If the sentence were negative ("If only we hadn't anticipated..."), the object would be forced into the partitive: Kunpa emme olisi ennakoineet tätä tilannetta!

Is the verb ennakoida related to the word ennen (before)?