What I want to understand is if there's a new money flow towards Bitcoin and alts, or it's just the same people trading for higher prices
it is both.
the same old people have gained a lot of money from previous altcoin pump and dumps. for example those who started participating in the altcoin pump and dump game with 1
BTC could have had 10
BTC in a short time last year during the same pumping season. so now they are again coming back in with the previous profit + some more money out of their pocket since last time it was successful.
also obviously bitcoin growth and all the adoption and all the media coverage has attracted a lot of new people. many of which are investing only. and when they get familiar with bitcoin they also find out about another market which is rising at the moment they found out about bitcoin. so without knowing they invest in altcoins too. and many end up losing a lot because they don't know what the pump and dump games in altcoins are.