Hello Sameer
This is a very good question. What is happening here is that R2 has obtained its original hop count of 1 to network 3.3.3.3 from R3. So since R3 has told R2 that the distance to 3.3.3.3 is 1, it puts it in its routing table.
After the procedure that is described, R3 sends a new hop count to R2 of 2. Now you say since this hop count is higher than that which is already in the routing table of R2, why does R2 replace it? Well, it will replace it because it is an updated piece of information.
So, the previous entry of metric 1 that was learned from R3 is replaced with the updated entry of metric 2 from the same source, namely R3.
I hope this has been helpful!
Laz