Past Continuous in place of Past Perfect

Hello Native speakers,

I have read that we have to use Past perfect to introduce an event or action that is in out of sequence. But look at the pargraph below.

"As the railway network spread across Britain, Cook's excursions became more ambitious. By the mid 1840s, he was conducting tours to Scotland, Liverpool, Newcastle and London. By 1855 Cook had organised tours for almost fifteen years and felt that he had enough experience to start venturing overseas."

The first sentence "Cook's excursions became more ambitious" sets the time(Lets say TimeX). The third sentence is perfect as it is saying"By 1855 Cook had organised" to denote the action is before the initial time(TimeX). The second sentence is confusing as it says "By the mid 1840s, he was conducting". Since this action also takes place before the initial time(TimeX), why the past perfect "he had conducted" is not used here. Even the author is to emphasize the ongoing process, he would have written "he had been conducting" in past perfect progressive.

So if the sentence is correct, does it mean that we can also past continuous for out of sequence event instead of past perfect if we are to emphasize the ongoing nature and is this grammatically correct?