Speculation of course but I would guess that the moving of the goalposts that he refers to is initially being told he was expected to change the style of play to one which would be used not only for the first team but also for all the academy teams and that he'd been given time for this change to bear fruit.
However, when his chosen approach led to relegation looking like a possibility, he was put under pressure to change his system and play 4-4-2 even though the players he (or more likely Stevenson) had recruited weren't necessarily best suited to that formation.
Pretty sure he'd have gone anyway but I think he'll have been disappointed that he wasn't allowed to stick to "the plan" - a plan which was meant to be the club's plan, not just his.
Given that said players have won 3 out of 6 since Weir departed as opposed to 1 in 13, that can't be right.