What does 早待不住了 mean in 要在往常，我一定早待不住了……? 要在往常，我一定早待不住了，惦记着某某侦探的案件是不是有了突破，……
Google Translate:  As usual, I must have been unable to stay any longer, wondering if there was a breakthrough in the case of Detective XX,...
标准教程HSK6上，87页

I don't understand what the part in bold above means.  Maybe it's something along the lines of &quot;As usual, I was definitely prematurely restless, ...&quot;.  It's not clear at all to me.
Question: What does 早待不住了 mean in 要在往常，我一定早待不住了……?
要是 signifies a hypothetical construction. 往常 does not only mean ‘as usual’ (which only corresponds to 常, as in 通常, 正常, 常規); 往 here specifies the past, as in 往日, 往事, 往昔. Together they mean ‘normally in the past’.

早 is an adverb meaning ‘already’. Think of that as saying, something happened well in the past (early in the timeline).

他早(就)離開了。 He left already.


待 is a verb meaning ‘to stay’. 不住 is an add-on to it, literally meaning ‘not to a still’. Figuratively, 待不住 means you can’t contain yourself, or you’ve got itchy feet. Perhaps you're excited or anxious about something.

The whole sentence means ‘I’ in the past would’ve not been able to control myself in coming up with the many racing thoughts in my head (unsolved cases, scientific breakthroughs, lottery etc.). My mind is so irritable that these thoughts would have occurred very easily and very soon (hence the use of 早). But now my mind is completely at peace, so they are nowhere to be found.