Why is there no VPN connection between networks without NAT masquerade?

Question

Computer networks

Hello, the question seems simple but I can't figure it out.
Here is an example network diagram

Router A client
Router B server

Router A receives ip address 192.168.1.10.
In the NAT chain, one masquerade rule per public interface to access the Internet.
In this configuration, router A pings router B. Computers behind router A cannot ping router B.

After adding a NAT masquerade rule to the VPN interface in router A, computers behind router A can already ping router B.

Why is it necessary to masquerade the VPN interface for access to network B ?
Why is routing not working? It seems private addresses should be routed?

Answer 1

In such a situation, you need a site-to-site vpn.
Cars behind router B have no idea where to look for cars from 192.168.2.0/24.
PS
Accordingly, the addresses at the ends of the VPN tunnel are needed, for proper routing, not from the same subnets, i.e. not 192.168.1.0/24 and not 192.168.2.0/24.

Answer 2

https://linkmeup.ru/blog/14.html