The second half of passage Jesus refers to the general mass, and generally speaking about have not 'seen', yet 'believe'.
Dear readers, disciple Thomas' specific mistake is our lesson in general, to all things pertaining to the Kingdom of GOD.
That is, we have not 'seen', yet 'believe', besides the disciples and followers were with Jesus for more than 3 years.
As in the case of Apostle Paul, wished he had been there during that time to 'witness' like them.
1 Corinthians 15:
8. And last of all He was seen of me also, as of one born out of due time.
For example, there those who seek 'signs' and 'wonders' in order to 'see' and 'believe', for instants the Jews.
On the contrary, there are those who have not 'seen' signs and wonders.
Yet, hearing Jesus' word/saying/teaching they 'believe' in Him.
And there are those who seek wise writings in order to 'see' and 'believe'. for instance the Greek.
On the contrary, there are those who have not 'seen' wise writings.
Yet, hearing Jesus' word/saying/teaching they 'believe' in Him
For we want to 'see' changes in our lives in order for us to 'believe'.
On the contrary, there are those who have not 'seen' changes in their lives.
Yet, hearing His word/saying/teaching they 'believe' in Him.
We want to 'see' GOD do either this or that for our prosperity, in order for us to 'believe'..
There are those who have not 'seen' Jesus either do this or that for their prosperity.
Yet, hearing Jesus' word/saying/teaching alone they already believe in Him.
Hence by faith hearing the Word of GOD alone, they're able to start from poverty or remain in poverty blessing others instead.
For me these are all the definition to what Jesus meant by, "Blessed are they who've not 'seen', and have yet 'believed'."
Hebrews 11:
1. Now faith is the substance of things hoped for, the evidence of things not 'seen'.