Salaam
Its quite simple - did the prophet tell the sahaba to collect the Quran in book form - the answer is no - so its a bida - but its a good bida as we believe Abu Bakr (ra) and Umar (ra) did the right thing clearly.
Peace.
Salam
Brother but this isn't an act of worship is it? They did not do it with the hope that they will gain rewards. You are interpreting the term bidah all wrong. If it were an innovation with the intent of gaining reward then that is deemed a sin. This wasn't an act of worship just merely preserving the holy words of Allah. Making it more accessible for the ummah.
Here are a few bidah's I came across in masajids I used to go to when I was naive...
1. Congregational dua (or the fact that they make it compulsory and perform it after every single salaat, some hurry through their salaat to join in on the dua, which is best done individually anyway)
2. 15th Shaaban
3. Milad-un-nabi (which can be compared to shirk seeing as many believe that the prophet (pbuh) is alive and he will be in our presence if we perform this act, and therefore we make dua to him instead of Allah (swt)
4. Verbal intention before prayer (naayitual nussalliya lillahi tahlaaa..... intention is in the heart it doesn't need to be made verbal, when you are going to eat you don't make a verbal intention now do u?)
5. wearing of the hat is compulsury but beard is voluntary (thought of general public not the mosques themselves)
6. on jummah they do a lecture/sermon first in the local language (note this is not the khutbah) Then they go on to do the kutbah in arabic even though no one understands it (they believe doing the kutbah itself in the local language is not allowed)
7. placing a death stone in the graveyard to ID the dead person.
8. grave worship - making dua facing the graves = grave worship im afraid.
These ones are of the top of my head, and im sure sadly they still exist in these mosques. I go to a salafi masajid now, and alhamdullillah I feel the sukoon, peace and fullfillment of my daily prayers now because none of these innovations exist.