"Math-hard" is not defensible in the US because the patent system has been weakened so much. VCs in the 1980s and 1990s looked for a strong patent position. VCs today look for a strong marketing position. VCs as a class made money in the 1980s and 1990s made money. That stopped working around 2000, when throwing money at something to buy market share took over.

(Yes, this will be modded down by the "IP should be free" crowd.)