Ortho, where is that quoted from? Which sefer is that recorded in?
Re, the rambam “if he has not succeeded to this point…”, Dying would be an example of failing. For instance, the Lubavitcher rebbe tried bringing jews back to Torah, one of the requirements in the rambam. Not only did he fail to do so, under his leadership, intermarriage only increased. Frum people became more populous because of having children; the BT movement barely made up for the OTD population.
The real BT movement, which were seeing now especially in eretz yisroel, is among sefardim and Israelis, and chabad is not the major player in that regard.
So during his lifetime, the Lubavitcher rebbe failed to bring back even 1/10 of klal yisroel back to Torah. The rambam says moshiach will bring all lf yisroel back, and that’s just to be bechezkas. He also will fight wars, physical wars, as evidenced ny juxtaposing moshiach with bar kochva, because BK was fighting physical wars.
Fighting spiritual wars was also a failure, because the world only became more secular under the time the Lubavitcher rebbe was a leader, not less. One anti religious country fell, but others grew, including China, which became more of an international player at the time.
Re, techias hamaysim and moshiach being among them – that’s what the abarbanel says, that moshiach can be from those who rise at the time of techias hamaysim, and the rishonim were unsure if TH will happen before or after bias hamoshiach.
But that would make the Lubavitcher rebbe no more likely than anyone else to be moshiach; I’ve also not heard any messianic Lubavitchers say that he will come back by techias hamaysim at the same time, but the rizhiner was a far greater person than the Lubavitcher rebbe, and if what you quote is accurate, I’d sooner believe the words of a universally recognized tzadik who said something will happen, over a controversial figure who many question even his tzidkus, and frankly his status as a member of shlomei emunas yisroel, due to the god in a body remarks.
If what you quote from the rizhiner is true, it’s also one opinion that is not mainstream. One of my rebbeim is a sadigerer chosid; he would quote the rizhiner all of the time, but never said anything of the sort. And he wouldn’t have shied away from it – i was a shtikel ben bayis by him for about 5 years.