How does google know if your websites are connected and punches all of the websites at the same time

I have a list of website that are hosted on the same place with the same one ip being used on that host for all of the websites but I also use cloud flare, I have built some backlinks manually using profiles and everything was going well I have started to notice some small improvement on my DA on Ahref.

but the number of backlinks that were detected were less than 20 while i have built more than 300 backlinks so I have decided to forced them to be indexed by creating some small articles on 2.0 websites that list 10 backlinks on each article.

I started by posting to articles. and then two days later when I was about to start posting other links on a new article I check my new visitors coming from google to notice that I have lost all the traffic coming from google.

and what is worst is that didn't just happened on the websites that I have built backlinks for or forced to be indexed it happened to all my websites including websites that I never create a single backlink for or did anything on them that could make google punch it for it.

my websites are on the same host that uses the same IP but they have could flare and I have whois guard actived to protect my information on the domains and I am not using google console in any of them. so I don't understand how did google link them together?

at the moment I want to know :

1. why did google did that - is it because of the indexing or the backlinks built manually on profiles
2. and how could google link my websites together
3. and what should I do to fix it.

thank you everyone for your time.