They weren't digitalized. They turned their organic essence and such into a fine powder that, if everything had gone correctly, would have been reformatted back into the individual Precursors. Unfortunately, the technology that would have done this malfunctioned and the ships carrying the powder were later found by ancient humans. After running some tests, the powder was deemed harmless and humans began feeding it to a domesticated species known as Pheru. After several generations, the Pheru began to have strange growths appear on their bodies, which other Pheru would proceed to eat. Around the same time, abortions/failed pregnancies became commonplace in the Pheru. It wasn't long after this that the Flood became as we know it today.

I heard they were a forerunner test for humans and other organic life?

What? Where the hell did you hear that malarkey?

The halo wiki. It said they wanted to test the advanced humans. I guess they failed and that's why they had to devolve or something

That's completely wrong.

Yea shore??