The answer to your questions are very many, and some. The numbers are of course relative, but consider the following:

During the 1980's early internet, white supremacist groups were among the first[0] to being using the new medium for organization and information purposes. They used it then to publish among other things a list[1] of "race traitors" etc including name, address, phone number, promulgate misinformation, gaslighting established norms and history (ex: Holocaust Denialism), and develop strategies for what can really only be described as terrorist indoctrination in many respects.

Some of the group involved killed a man with automatic weapons and hijacked an armored car with millions in cash to finance a separatist uprising. One of these was Louis Beam[2] who was a quite violent seditionist, and developed the "lone wolf" militia cell structure which is familiar today. Beam used these telecommunication/internet networks to create and distribute a lot of white separatist information. His activity goes on and on, it is quite vile in all respects. He has been charged and acquitted of sedition.

In this academic piece by sociologist Chip Berlet[3], he recounts attempting to counteract the white supremacy BBS with an anti-racist BBS at an Anti-Klan symposium. The understanding of BBS was quite poor at the time. By the 1990's the white-supremacist BBS network had grown quite a bit, distributing newspapers and operating file transfer and messaging services into a national network of neonazi BBS including Stormfront[4], which is of course still in operation, and is quite influential. They successfully transitioned to the ordinary internet and also AOL, using them as very effective recruitment tools.

Neonazi/white supremacist/separatist/seditionist groups have used the internet very effectively pretty much from the beginning. Perhaps this is an effect of Johnathan Gabriel's Greater Internet Fuckwad Theory[5] as well as some kind of operationalized Poe's Law--race rallys thrive in protective shade. KKK marches and the like are routinely confronted by anti-racist counter-protests, but the current nature of online discourse continues to provide an asymmetric advantage to these types of activities. The old "Filter Bubble" doesn't lend many opportunities for normal people to insert themselves in the radicalization process...this could possibly be better than worse.

The literature on this is vast, exploring how a normal person can become radicalized into a racist white separatist is a strange rabbit hole to descend.

There exists a kind and inspiring man named Daryl Davis[6] who is pretty good at converting KKK/supremacists (he has many surprising success stories) away from this kind of behavior, but notice how his methodology requires a personal touch and much compassion. How many "more people saw that and immediately criticized the neonazis who wouldn't have seen them before?" is not a very good discriminator for this activity at all. Effectively, "None" is the real answer to your question.

The fact of the matter is that toxic memes and divisive trolling are consumed by people while on the can, idle-ly (or perhaps compulsevly) skimming social media and whatnot. The uncritical ingestion of this kind of thing simply habituates people to these kind of beliefs. I don't think a person who has fallen for this stuff is necessarily bad at first blush, and surely have many possibilities for redemption, but the effort required is really not the kind that is easily rallied.

It's a complicated notion, but it boils down to the fact that you have to fight Hate with Love.

[0] - https://timeline.com/white-supremacist-early-internet-5e9167...

[2] - https://www.splcenter.org/fighting-hate/extremist-files/indi...

[1] - https://www.nytimes.com/1985/02/15/us/computer-network-links...

[3] - http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.552...

[4] - https://en.wikipedia.org/wiki/Stormfront_(website)

[5] - (original source unavailable) https://en.wikipedia.org/wiki/Penny_Arcade#%22Greater_Intern...

[6] - https://www.theguardian.com/music/2020/mar/18/daryl-davis-bl...