I wonder whether the past tense is interchanged with the present tense

The reason I stopped smoking was that all my friends had already stopped smoking.

The reason I stopped smoking is that all my friends had already stopped smoking.

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I wonder if the verb "was" is replaced for "is", which reflects the present time. I think it's not possible because the time I stopped smoking was the past, and the cause inspiring the determination to stop smoking was also the past thing.

Is it right?