The Inflation Reduction Act
No it was way more complicated than that. Manchin killed the last bill because he had concerns about the fact that it didn't tax the rich enough and that he didn't like the temporary programs (in particular the Child Tax Credit, which was only extended for 1 year because of a compromise deal with him because he didn't like it). At least that what he told a WV radio show host back in December.
Then after months of saying he's willing to continue talking and ignoring people's requests to restart negotiations to instead tell people that those negotiations aren't happening, he laid out a climate, drug price, and deficit reduction bill that he said he wanted to pass. This would be funded by tax increases, and according to him the deficit reduction was the "best way" to fight inflation. This was what he urged the Democrats to do in response to inflation.
Then two more months pass and when it looked like talks were restarting in May on that very bill Manchin wanted everyone to pass, Manchin out of the blue sidelined those talks for bipartisan climate talks with people who don't believe in climate change. The only thing bipartisan agreement he managed to get was for both sides, Democrats and Republicans, to come into the same room and agree that this was all pointless. That shaved off an entire month off the clock when Democrats were urging Manchin that there wasn't much time left, and set the stage for the time crunch we saw in July.
And just when it looked like things were finally about to come to an agreement, Manchin suddenly had a realization that because of concerns about inflation he cannot do the tax increases in the bill which would've hindered the deficit reduction funding in the bill which would've, according to Manchin's own metrics, hindered fighting inflation. In exchange he was willing to do a temporary health care bill instead, because if the BBB bill negotiations taught us anything, he was perfectly fine with that.
And now he's kind of reversed that last position. I suppose somebody came up to him and told him that it was his own inflation fighting bill and he came to his senses. Either that or because the Democrats played the Republicans (a rare instance) because they threatened to block the CHIPs bill from passing if they realized that the Democrats were trying to cut the deficit. I mean, they just blocked veteran's aid because of it so yeah.
All in all, Manchin is a fucking nightmare to negotiate with. But he was the reason why the bill was kept up for so long and given the state of most of the congressional Democrats, then I imagine they're willing to just take what he's offering them. The only wildcard is Sinema who seems to love holding corrupt shitty positions and not telling anyone about it. Then again the bill was designed around her strict tax demands, she's stated she won't change her position in this new round of negotiations months ago, and she apparently seems to genuinely care about the climate stuff in BBB. Then again she's also a diva so who knows.