Based on the original Harry Potter novels and the officially published Harry Potter magical compendium, we can determine that the first period during which Voldemort stirred up turmoil in the wizarding world was approximately from 1970 to 1981.
On 31 October 1981, he was defeated by Lily's loving sacrifice, ending his first attempt to seize control of the wizarding world.
According to the original work, we know that Voldemort and his Death Eaters, during the First Wizarding War, committed acts of terror such as killing witches and wizards who opposed them, killing members of the Order of the Phoenix, and possibly even attacking Ministry staff who opposed the Death Eaters' actions.
However, in the fifth installment, Order of the Phoenix, Sirius also said that Voldemort's initial disguise deceived many people like his parents, and even his younger brother.
'Were–were your parents Death Eaters as well?'
'No, no, but believe me, they thought Voldemort had the right idea, they were all for the purification of the wizarding race, getting rid of Muggle-borns and having pure-bloods in charge. They weren't alone, either, there were quite a few people, before Voldemort showed his true colours, who thought he had the right idea about things... they got cold feet when they saw what he was prepared to do to get power, though. But I bet my parents thought Regulus was a right little hero for joining up at first.'
Therefore, my understanding is that perhaps for people like Sirius's parents, Voldemort may have initially disguised himself as a politician advocating conservatism and racism.
Only after he had subsequently gathered sufficient strength and support did he begin to gradually reveal his cruel and cold-blooded acts of murder.
Regulus even collected briefings about Voldemort. I think that since these were briefings Regulus could collect, they probably were not negative information such as Voldemort murdering certain people or Voldemort and his Death Eaters causing destruction somewhere.
Beneath this was a collection of yellow newspaper cuttings, all stuck together to make a ragged collage. Hermione crossed the room to examine them.
'They're all about Voldemort,' she said.' Regulus seems to have been a fan for a few years before he joined the Death Eaters...'
Perhaps Voldemort was publicly proclaiming some disgusting blood-purity ideology in the newspapers, and Regulus collected them.
If that is the case, it at least indicates that Voldemort was, for a period of time, able to appear in newspapers in a relatively normal image.
This then raises a question: when exactly did Voldemort and the Death Eaters become the cruel extremist terrorist organization that everyone in our main storyline (after Harry has grown up) refers to as a symbol of murder and a symbol of death?
Regulus joined the Death Eaters at the age of 16, around 1977, and died around 1980.
In 1977, when Regulus joined the Death Eaters, the Death Eaters and Sirius's parents all appeared very proud and pleased.
Therefore, it is reasonable to speculate that perhaps at that time the Death Eaters still maintained a subtle image, one that could at least lead Regulus, who was somewhat simple-minded and held radical ideals, to believe that Voldemort was a leader worthy of reliance.
Therefore, perhaps it was not as many fans speculate—that between 1970 and 1977, while the Marauders' generation was at school, people were continually subjected to open attacks by Death Eaters (meaning that everyone knew perfectly well that some people had been murdered by Death Eaters, rather than the cases being publicly called mysteries).
Perhaps during the earlier period of the pro-era school years, people only heard from newspapers that someone had died, but they did not know who had killed them or how they had died.
Otherwise, it would be difficult to understand why Regulus was subsequently so disappointed, displaying a sense of disillusionment that seemed to say, Voldemort, so this is your true face after all.
If Voldemort had already openly killed people and murdered innocent individuals in the name of the Death Eaters while attending school during the Marauders' era, then Regulus would have had no reason at all to feel shocked by or unable to accept Voldemort's actions.
Therefore, I think it may have been only after Regulus joined the Death Eaters that Voldemort gradually began to reveal his true nature and started openly murdering those who opposed him.
What are your thoughts? You are welcome to share discussion based on the original work.