Snead has explained the Rams draft process many times. It's a wee bit more complicated, and slightly more nunced than Best Plater Available vs. position of need. To take it just one baby step further, it's both/and, not either/or.
They evaluate players and assign values to a broad range of prospects (the players on their board) based on the factors they consider important. Thus, an offensive tackle may score lower on their rubric than a defensive linebacker according to their criteria. The highest valued player availible, when they're on the clock, might become their choice. If that players might still be available later they might choose another highly-valued player, and stay put or trade up or down to get that player or others of equivalent value. The BPA, according to fan and pundit estimates, may not be the best fit on the Rams rubric.
The above is my simplified understanding of the Rams scouting and draft process - and it's like one facet of a many-sided stone that we call roster building.
And Snead and the Rams are pretty good at it.
