Wasn't the conspiracy theory that truecrypt got shut down because it was 'too effective', and the successor projects presumably have intentional backdoors or something?

Truecrypt was likely developed by only 1 man, Paul le roux, who likely shut it down because he was on the run for being an international drug/human smuggler/cartel member. It’s kind of a crazy story.

But either way both truecrypt and veracrypt were independently audited and no major flaws were found. Not sure when the last veracrypt audit was done.