What is required for a HSRP failover?

In laymans terms. I get a physical disconnection or port shutdown will do it, but I am trying to understand a lab setup where traffic arrives at the "secondary" router and it re-converges through that.

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So say-

Router 1 = 192.168.1.1

Router 2 = 192.168.1.2

HSRP virtual= 192.168.1.3

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So the primary interface is still "up" as it is connected to a switch interface, but there is a switchover further back, and the traffic is still being sent to the 192.168.1.3 address. But physically, the only way it can get off the network is via the connection to router 2.

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So does HSRP recognise this 192.168.1.3 addressed traffic arriving on the secondary router interface (.2) and go "hey, this should be on the other interface, but obviously something is wrong, so I better fail over" ?

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Edit: topology here https://i.imgur.com/MAUZGpv.png