No no, it's not about nationality.
The problem is that Inter spent a great deal of time, financial planning and strategy work to devise a way to buy Lukaku and ensure him a top tier salary.
Keeping also in mind that his last season was lackluster to say the least and that the main reason they were doing this extra mile for him was that he always displayed a strong desire to be part of the team.
And then when finally they found a way to make it work, he was not picking up the phone anymore and showing by also waiting for Juventus'answer that all he said was just pretty much lies. The management got really angry, I've never seen such reaction before, I suspect that they really felt insulted far beyond the standard business/trading play between parts.
Exactly, he was/is actually closer to signing with some Arab team than Juve.
But for Inter fans Juve is more outrageous and journalists preferred that angle for selling the news.