されてきた

has been

→ 為る
phrase Rare #33,412
has been Passive form followed by てきた, often describing something that has happened or been the case over time up to the present.
JA: この町では多くの古い建物が保存されてきた。
EN: Many old buildings have been preserved in this town.

彼との連絡が可能になり救出計画も具体化されてきた

We were able to get in touch with him, and the rescue plan has also begun to take concrete shape.

— オデッセイ (2015)

アメリカの多くの州で死刑は廃止されてきた。

The death penalty has been abolished in many U.S. states.

この車は乱暴な使い方をされてきたに違いない。

This car must have been treated roughly.

そうした事態が起きるたびに、海のナポレオンは阻止されてきた。

Each time something like that happened, the Napoleon of the Sea was stopped.