Complex sentence: After the German invasion of Hungary, the Peace Party with other parties established the Hungarian Front, the party's potential allies were still very wary of them, therefor the popular front was never able to win much support amongst the populace.
Split into simpler sentences: After the German invasion of Hungary, the Peace Party with other parties establishing the Hungarian Front, the party's potential allies were still very wary of them. Therefor the Popular Front was never able to win much support amongst the populace.