I don't think it's at all ridiculous. Just like I grew up in Harlem New York and lived the evolution of Hip-Hop, and while great in his own regard, there is no way in hell Biggie Smalls was the greatest rapper of all time, and even less, his once good friend turned enemy 2Pac. Biggie was considerably better in all but one facet and that was running his mouth rather ignorantly because no one did that better than 2Pac.
However, millions of people bought into the hype their personal battle created which was all-out war that ended in the murder of one of them and the other met his demise because he couldn't bring himself to stop acting like an ignorant "Thug" he was aspiring to be. From a ballet aficionado to a comedic rap group's puppy dog groupie, to hawrdcwore Nigga! after a role he landed without intending to which IS what he molded his persona after. And to be be clear, there isn't a single greatest rapper of all time, but there is a handfull of guys who are that almost equally, with the pendulum leaning towards 2 more than any others. Eminem and Busta. However, saying that around a group of people who bought into the hype of the media, spawned by their premature deaths, and you might as well be speaking politics because in their minds what they've been conditioned to believe just is and to entertain anything different is lunacy, even though the material is there to be gone over.
The same is true of Senna and when it comes to Jochen Rindt, even more so. I'll say he's absolutely most overrated championship winning driver of all time and only because he was crowned WDC posthumously. THAT is sadly his real claim to fame. He was at best decent in decent cars and he died 4 with 4 races to go driving a Dominant Lotus-Ford that made him look better than he was, but the 1970 season was so erratic in terms of drivers actually finishing races that any driver who made it to the finish line towards the front consistently had a shot of winning. luckily for Rindt his Lotus proved more reliable than most other front runners.
Now Jim Clark is completely different animal. And by animal I do mean ANIMAL. So good was he that drivers would be perplexed at how he took corners so fast that he'd literally explain to them exactly how he was able to do so and would then jump in his car and have them follow him around the track at moderate speeds so they could see and learn his line before going all out for blistering laps and they STILL couldn't match his time.
The only other sports figure I know to have done this was Dion Sanders. As a cornerback (his first position - the greatest ever there) he'd tell wide receivers how to beat him and when they'd finally get tired of him destroying them and would finally listen, they'd burn him, thinking they had him beat, only to have him make the adjustment and run around them to either break the play up or make an interception. When converted to a wide receiver He'd tell cornerbacks how they should cover him and would then tell them the route he was running and STILL there was nothing they could do to stop him.
In F1 the only other driver that was that much better than his contemporaries was Michael. Heck, they even had complete telemetry and still couldn't match him. Senna was close to this but a good deal of his amazing laps where he passed several people were only possible because drivers didn't want to end their races prematurely. Excluding wet races of course because Senna was almost always untouchable in wet conditions.

Upon his death, Senna was elevated to legendary status effective immediately, and anyone who disagreed with that either hated the guy or was talking nonsense.
he died. I don't think his reputation suddenly grew afterwards