> NAT became a poor-man's firewall and effectively blocked peer-to-peer connections making it difficult to host a server at home.

Most ISPs (with the exception of very small ones) until recently assign one public IP address per customer and NAT is done on home router. With this setup it is not hard to host a server at home - it is just one rule on router to NAT all incoming connections to that server. Many SOHO routers support such setup. Alternatively, the server can just work as a router.

> This incentivized early ISPs to offer only asymmetric connections that pushed users towards a consumer-only service that crippled early Internet protocols.

Asymmetric connections are offered because many last-mile technologies (like ADSL and cable modem) are asymmetric on link-level - they use different bandwidth allocations for upstream and downstream.