not that many people did buy the ibm pc on launch, because you're right. it was released in mid-01981, and sold less than 200'000 in 01982. the commodore 64 sold 360'000 in 01982, and it wasn't even released until halfway through it. apple was selling a billion dollars a year that year, entirely from the apple ][ line; it wouldn't introduce the lisa until the next year. so that's on the order of half a million apple pcs shipped in 01982

i think ibm's reputation was a pretty important factor, not so much for making people buy it (though it did do that) but for convincing them that other people would buy it. it's easy to forget in 02024 just how dominant, and how malignant, that ibm was in the computing world at the time. they'd built aiken's first computer at harvard, they'd introduced ascii (then spent decades battling it—the pc was their first ascii product), they'd invented fortran, they'd invented relational databases (but kept pushing ims), they'd provided the hardware lisp and timesharing were developed on, and they utterly owned business computing, more thoroughly than microsoft does today

pretty quickly there was a lot of software out there for it. partly this was because programmers were convinced that users would buy it, but also, it was easy to port cp/m software to it. at a time when 'serious' pc software was almost entirely in assembly, you couldn't do that with the apple ][+ (unless you bought another computer from microsoft to plug into one of its slots to run cp/m). also, it was easy to make peripherals for it (though this was just as easy for the apple). and microsoft licensed ms-dos to other vendors like tandy and zenith, resulting in not-quite-compatibles like the z-100 (01982), the dec rainbow (01982), the tandy 2000 (01983), and the sharp pc-5000 laptop (01983). the software written for those machines was also usually easily ported to the ibm pc

you know how ebay and airbnb are utterly dominant because they own a two-sided market? if you want a place to stay, you go on airbnb because that's where the listings are, and if you want to rent out a place to travelers, you list it on airbnb because that's where the travelers are? the ibm pc owned a three-sided market: users, software vendors, and peripheral vendors. not at first, of course, but pretty soon; the s-100 systems weren't that dominant in a market fragmented between apple, commodore, atari, osborne, kaypro, etc.

then, once compaq came out with their ibm-compatible portable computer in 01983, ibm didn't own the market anymore. even less once phoenix started selling their bios in 01984. and that was what really made the ibm pc catch on: no single company's missteps could sink the platform the way commodore did with the amiga and the way apple did with the iigs's successors. ibm did in fact try to avoid introducing an 80386-based ibm compatible in order to avoid cannibalizing their minicomputer and mainframe lines, just as apple did with the iigs, so compaq beat ibm to market in 01986. by like a year!

there are also technical questions. the 8088 is a lot faster than the 6502 at running compiled c, especially with the crappy compilers of the time. it's also noticeably faster at numerical code. and the apple ][+ was running its 6502 at 1 megahertz, not 2. the beeb not having slots was a fatal flaw for much of the market; it turns out there are really a lot of peripherals that work badly over a serial port

and once ram prices came down a bit, 640k of ram became standard; the macintosh shipped with 128k in 01984 and quickly changed that to 512k. using 640k of ram on the 8088 was a lot easier than using it on a 6502, although intel's braindamaged segmentation scheme (avoided on the iigs's 65816) forced you to use 'garbage kludges' like lim ems (01985) to use more than a megabyte at all. that there was so much pressure to be able to use more than a megabyte as early as 01985 should tell you something about how far memory prices had come down and how important it was that the 6502 and 8085 couldn't handle more ram