1) [...] Something at this time meant that he reconsidered his approaches to Saidit

Have you got something to support this? Can you expand on what /u/magnora7 said and what you mean?

1) [...] and let Amelia and d3rr take over at that time.

/u/magnora7 didn't "let" them - he disappeared and by default abandoned SaidIt. /u/TheAmeilaMay was helping deal with spam and became by default the only active admin. /u/d3rr had already quit unhappy with how /u/magnora7 was managing things, but to his credit /u/d3rr remained available for technical emergencies. In the first week /u/TheAmeilaMay messed up things enough that when /u/d3rr offered to step in she stepped aside and things have been running smoothly under /u/d3rr since, so far as I know.

2) [...] particularly with regard to Saidit, but look at what's happening at other so-called "fee speech" [sic] right-wing websites.

SaidIt is NOT a right-wing site. Originally called AntiExtremes.com, SaidIt is very much a centrist site and both founders, M7D3, do not consider it a free-speech site because it attracts asstrolls. Truth-seeking and free-thinking are some of the more appropriate terms you may use.

2) [...] A letter from one of these people is very easy to arrange, or from the CIA or the FBI, regarding hate speech or whatever.

I'm very skeptical of this. If they wanted to they could squash SaidIt.

2) [...] It's also possible that there are legal problems with Saidit, and if so, M7 can't say anything during the legal process.

This is a more practical and possible theory.

2) [...] This is enough to change anyone's one's approaches in this manner at Saidit.

He didn't just "change approach" - he disappeared, without a word, 4 months ago.