What is the difference between Has been and Has Tom been able?

Question

I have a grammar question. What is the reason or rule why these two sentences are different?

Only by working hard has Tom been able to go far in his job.

Only by working hard Tom has been able to go far in his job.

I am a teacher and I need to explain this to my student in the next few hours. Please if anyone who knows grammar please help me understand what the difference is so I can tell my student. Thank you very much and only serious answers please.

Answer 1

Both sentences are correct. There isn't any difference if you write it down. The difference is in spoken english. There are some sentences you have to pronounce with more emphasis, because they are important. And you under-pronounce a word which is not that significant.
Like in the first sentence, you would pronounce TOM with a more raised voice, because then the emphasis is on the SUBJECT.
Whereas in the second sentence you would pronounce HAS with more enunciation. Because here the emphasis is on TOM'S HARD WORK which resulted in his success.
This method is called intonation, you have to watch out for ACCENTS and DESCENT in a sentence.
Hope this helps.

Answer 2

I know this one too..but like you I fail at explaining it.

It has something to do with one being an unbreakable sentence construction and the other actually being two.