Remember!!

[Al-Baqarah: 251]
And if it were not for Allah checking [some] people by means of others, the earth would have been corrupted, but Allah is full of bounty to the worlds.

[Al-Baqarah : 253]
If Allah had willed, succeeding generations would not have fought against each other, after clear Verses of Allah had come to them, but they differed - some of them believed and others disbelieved. If Allah had willed, they would not have fought against one another, but Allah does what He likes.