The people of Israel, the Children of Israel, have endured 400 unexplainable years twice in Biblical history.

First, 400 years of slavery in Egypt, and the only explanation given is that another Pharoah came to power that did not know Joseph—Joseph, who was responsible for saving his family of 70 Hebrews from famine and bringing them to Egypt.
Don’t know why He waited, but God acted supernaturally after all those years to rescue and deliver His People, and He gave them a rallying cry to remember forever—The Passover.

Again, after the last prophet, Malachi, the Children of Israel did not hear a word from God through another prophet for 400 years.
Don’t know why He waited, but God acted supernaturally after all those years to rescue and deliver His People, and all people, and sent His Son, Jesus, to save us from our greatest bondage, sin.

We can’t explain God, because He is God—His ways and His thoughts are higher than ours.
But we can take Him at His Word, and take what Jesus did for us, and have our biggest problem taken care of, and have a reunited relationship with Him forever.