It took longer than necessary, but in what ways do you think an Intel Core-derived chip is different from what an “Intel Alpha” would have been?

Taking for granted that hardware backcompat (Itanium had this, too!) was a starting requirement…

Wasn't there a problem with Alpha, that it had too weak memory model or something? Think of atomic instructions with multi CPU system. Or do I remember something wrong?

Alpha was great but that wasn't enough against the convenience of just running an x86 box. It didn't find a niche quickly enough. ARM survived because they were low power. POWER survived because IBM is one big niche. MIPS died and reincarnated into RISC-V. I have no idea where Alpha would have gone had it not been dropped.