Spam was a massive problem long before big tech existed.
- The old USENET network which was/is a federated ecosystem of servers run by universities etc was overrun with unwanted spam.
- Compuserve dialup network was blocking spam and they were also involved in a 1997 court case (1997 is a year before big tech like Google Inc existed in 1998.): https://en.wikipedia.org/wiki/CompuServe_Inc._v._Cyber_Promo....
- the infamous "spam solutions" webpage that was a snarky attempt at "educating" people about fixing spam was created around February 2004 which was 2 months before Gmail service was introduced: https://craphound.com/spamsolutions.txt
Other "small" areas of the internet are also universally hit with spam abuse:
- blogs that allowed "readers' comments and feedback" got inundated with spam and the blog owners added CAPTCHAS or disabled comments completely.
- small web forums like vBulletin and phpBB forums got hit with spam and admins put in "email signup and valid email verification link" workflows.
- even the newer modern decentralized communication networks like Nostr attract spam: https://old.reddit.com/r/nostr/comments/121ytwf/cutting_thro...
The existence of a big player like Gmail that was introduced in 2004 is not the reason for "so much spam".
Spam volume is always a problem on any communication network where the cost to create new identities is $0 and the cost to send messages is near $0.00. An extreme example of the opposite situation is Bloomberg Terminals chat system not having a spam problem. Why? Because it costs $25000 a year subscription to use. Bloomberg did recently "unbundle" their chat system for a lower price but the point is that the friction for new accounts is still high enough to deter spam abuse.