[bjacogaerllyo]

Let me attempt to explain it simply, so we can easily understand:

I heard this in a lecture:

Someone who is sitting down doing nothing, will not make a mistake.

But a group of people who are literally carrying the world on their shoulders (by the Will of Allah) [i.e. the Sahabah ], they are only human, so they will make mistakes sometimes.

And since they are in such high positions, their mistakes will tend to affect more people and have more consequences than someone who makes a mistake and it only affects him or his household or something of that sort.

So they simply made a mistake or two in their lifetimes. Everyone makes mistakes. When me and you make a mistake, it is a small tiny one and it only affects ourselves and maybe a few people. But the higher up you are, the bigger the mistake seems to others. In the end, the sahabah made ijtihad and some were correct, some were incorrect, but all still deserve our praise.